FENTON, WILLIAM, M.A. DECEMBER 2019 PHILOSOPHY

ON THE PHILOSOPHY AND PSYCHOLOGY OF REASONING AND RATIONALITY (67 pp.)

Thesis Advisor: David Pereplyotchik

Many theorists in philosophy and psychology have held that reasoning is a capacity geared towards getting at truth and epitomized in logical deduction. Though this remains a prevalent view, it has recently been called into question by psychological research on biases in human reasoning. Hugo Mercier and Dan Sperber challenge both of these views and provide an alternative account of the nature and function of human reason. I will outline the grounds for holding that their "Interactionism" fits best with what is known about the evolution of human reasoning. Robert Brandom’s theory of rationality coincides with Interactionism in stressing the social nature of rationality, and in rejecting the notion that deduction is the key to understanding human reasoning. Although Brandom’s view has many virtues, it is not empirically informed.

This raises questions about whether Brandom's theory can stand up in light of the putative success of Interactionism. I will argue that, far from being rival theories of the same subject matter, Interactionism can usefully supplement Brandom's theory of rationality, thereby correcting some of its deficiencies.

ON THE PHILOSOPHY AND PSYCHOLOGY OF REASONING AND RATIONALITY

A thesis submitted

To Kent State University in Partial

Fulfillment for the

Degree of Master of Arts

by

William Fenton

December, 2019

© Copyright

All rights reserved

Except for previously published materials

Thesis written by

William Fenton

B.A., Kent State University, 2016

M.A., Kent State University, 2019

Approved by

______, Advisor

David Pereplyotchik

______, Chair, Department of Philosophy

Michael Byron ______, Dean, College of Arts and Sciences

James L. Blank

TABLE OF CONTENTS……………………………………………………………………..…iv

ACKNOWLEDGEMENTS…………………………………………………………………….vi

INTRODUCTION………………………………………………………………………………1

CHAPTERS

1. Formalist Approaches to Human Reasoning

§1 Introduction…………………………………………………………………………………7

§2 The Rejection of Psychologism……………………………………………………………..8

§3 Rudiments of Formalist Thought…………………………………………………………..10

§4 Mental Logic Theory………………………………………………………………………13

§5 Dual Process Theory……………………………………………………………………….16

§6 The Language of Thought Hypothesis……………………………………………………..21

§7 Conclusion…………………………………………………………………………………23

2. Inferential Materialism and Logical Expressivism

§1 Introduction………………………………………………………………………………..25

§2 Sellars on Material Rules of Inference…………………………………………………….27

§3.1 Logical Expressivism……………………………………………………………………34

§3.2 Semantic Inferentialism………………………………………………………………….36

§4 Conclusion…………………………………………………………………………………42

3. Inferentialism and Interactionism

§1 Introduction………………………………………………………………………………...44

§2 The Interactionist Theory of Reasoning……………………………………………………44

§3.1 Connections ……………………………………………………………………………...50

§3.2 Normative Pragmatics……………………………………………………………………52

iv §4.1 Reasoning and Mentalese………………………………………………………………..55

§4.2 Reasoning and Modularity………………………………………………………………57

Conclusion ………………………………………………………………………………………60

REFERENCES…………………………………………………………………………………..64

v ACKNOWLEDGEMENTS

Many thanks to David, Dr. Deb, Dr. Aldea, Dr. Zavota, Dr. Fernandez, Dr. Pendleton, Dr.

Barnbaum, Dr. Byron, Dr. Ryan, Dr. Ikuenobe, Dr. Kim, Alex Haas, Brant, Cara, Matt, Alex

Martin, Stan, Nikita, Griffin, Jared, and Nick.

vi On The Philosophy and Psychology of Reasoning and Rationality

Introduction

Formalism is the dominant view about rationality in philosophy, psychology, and cognitive science.1 The idea is that reasoning is a formal-computational process in the brain, geared towards the acquisition of true beliefs. Formalist approaches in psychology include mental logic theory, which seeks to explain our deductive reasoning capacities in terms of innate inference rules (Braine 1978; Braine and O’Brien 1998; Rips 1983, 1994), and dual process theory (Evans and Over 1996, Stanovich 1999, Kahneman 2011). Dual process theory holds that rational thinking—i.e., deduction and probabilistic reasoning—is a job for System 2, the slow, lazy, and sometimes rational part of the mind, while System 1 is in charge of fast, automatic, associative, intuitive processing. In philosophy and cognitive science, this idea finds its expression in the language of thought hypothesis, and the standard formulation of the computational theory of mind, according to which thoughts are represented by logically structured physical symbols in the brain (Fodor, 1975, 1987). To be clear, when I speak of the

“formalist” in this paper, I intend to be referring to a wide swath of theorists—not only to those who subscribe to the language of thought hypothesis, mental logic theory, or dual process theory,

1 There has been a recent shift in the psychology of reasoning away from the “deduction paradigm,” and towards the “the new paradigm” (see Elqayam, Bonnefon, and Over, 2016). Although the probabilistic and dual process approaches that fall under the heading of the new paradigm are not logic-centered, they are still formalist, as that term is used here.

1 but more generally to any view that takes human reasoning to be formal in nature, or understands rationality narrowly in terms of adherence to formal rules of inference.

In spite of the popularity of such views, I think that they are premised on questionable assumptions about the nature of reasoning and rationality. My critical aim in this essay is to motivate skepticism towards three formalist tenets in particular:

(i) the hypothesis that reasoning is formal in nature, and carried out by the internal manipulation of symbols in accordance with formal rules of inference, (ii) the assumption that reasoning is primarily a solitary activity, geared solely towards the acquisition of true beliefs, and (iii) the formalist conception of rationality according to which agents are rational so long as they draw formally valid inferences, and irrational when they fail to draw such inferences.

These ideas are interrelated: (i) is the central claim about reasoning present in all formalist theories, and it lends an air of plausibility to both (ii) and (iii) since it makes no mention of the environmental context that reasoning evolved to function in. Rather, (i) simply describes reasoning as an internal, formal psychological process, and since cognitive processes are private

—in the trivial sense that there aren’t other agents inside of our heads while we reason—the solitary picture of reasoning and its putative function mentioned in (ii) seems intuitively correct.

The standard of rationality invoked by (iii) is then jointly supported by both (i) and (ii). If reasoning is an internal formal-computational process, then it's not clear what purpose it might serve other than to produce true beliefs through formally valid inferential processes, and the failure to do so would appear to show that one’s reasoning skills are inadequate.

The reader should bear in mind that it is the formalist paradigm that I am attempting to motivate skepticism towards in this essay. It is—of course—rational to have true beliefs, and beliefs are no doubt the outputs of inferential processes. The alternative view of reasoning and

2 rationality pieced together in ch. 3 is compatible with both of these claims. It differs, however, with respect to the characterization of the inferential processes involved in reasoning, and it is skeptical with regard to the conception of irrationality assumed by those working under the formalist paradigm. While it is certainly rational to produce formally valid arguments with true conclusions, it’s not obvious that we should always characterize the failure to do so as irrational behavior.

For one thing, we should expect reasoning to fail, as it typically does (see ch. 1, §5), in contexts for which it is ill-suited in an evolutionary sense. This is one of the major lessons of the interactionist theory of reasoning (ch. 3, §2). Furthermore, materially valid arguments of the sort discussed in ch. 2 are not formally valid, but we would not characterize, e.g., the subjunctive inference from ‘X is a pen’ to ‘X would not disintegrate into thin air if I were to use it to write my signature’ as irrational on account of its not being a formally valid inference. And as Sellars points out (ch. 2, §2), we cannot say that our reason for endorsing such inferences is that they are enthymemes—that their true, “hidden” structures are formally valid. Considerations of this sort ought to motivate skepticism towards the idea—thesis (iii) above—that drawing formally valid inferences is the sole measure of human rationality. If what are clearly correct instances of reasoning do not qualify as rational by formalist standards, then it is not ordinary human reason that is inadequate but, rather, the formalist conception of it.

My constructive aim will be to piece together two strands of theorizing that I believe jointly comprise a satisfying alternative approach. The primary contribution will be to integrate

Robert Brandom’s semantic “inferentialism” with a promising new proposal in cognitive science

—viz., “interactionism,” as developed by Hugo Mercier and Dan Sperber in their 2017 book, The

3 Enigma of Reason. Although these theories differ in terms of methodology, inferentialism being a purely theoretical project, and interactionism an empirical hypothesis, I will argue that they are in agreement on fundamental points, and furthermore, that what is lacking in each can be provided by the other.

The core tenet of Brandom’s inferentialism is that meaning consists of the inferential relations between judgments and the concepts that constitute them (ch. 2, §3.2). Interactionism

(ch.3, §2) is the view that reasoning is a modular process of intuitive inference, which evolved for the purposes of producing and evaluating arguments. Significantly, these theories share two core commitments: (i) reasoning is not formal computation, and (ii) it is first and foremost a social activity; only derivatively a solitary one. I will argue that these commitments are sufficiently far-reaching to provide a rich common ground from which a hybrid view can be developed. One upshot of doing so is that it illustrates how Brandom’s inferentialism— developed entirely on the basis of theoretical and normative considerations—can be usefully combined with, and thereby supported by, an empirically plausible account of how human rationality actually came to be. In addition to knowing “what it is to do the trick,” we would also have a story about how “the trick” is actually done by flesh-and-blood humans, and how it came to be this way.

To be sure, Brandom is not himself interested the empirical details of reasoning and rationality, but rather in “conditions at once more abstract and more practical, which concern what we are able to do, rather than where we come from or what we are made of” (1994: 4). But as we’ll see in ch. 3, the relevant empirical details are available and, as far as Brandom’s project is concerned, promising—Mercier and Sperber’s interactionist theory is a well-motivated

4 empirical account of reasoning, and their findings appear to vindicate Brandom’s views on the nature of reasoning.

The benefits of developing a hybrid view, however, don’t flow only one way—from interactionism to inferentialism. Brandom, too, has something to offer. Mercier and Sperber plainly need an account of social norms—particularly, socio-normative statuses, such as commitment and entitlement—but provide little in the way of such an account in ER. Brandom, by contrast, has on offer a theoretically rich, coherent, and independently motivated account of precisely these notions. My suggestion in ch. 3 (§3.2) will be that Mercier and Sperber can fruitfully supplement their interactionist theory with Brandom’s pragmatic account of the above- mentioned normative statuses.

Brandom’s inferentialism takes over where Wilfrid Sellars left off. In his 1953 paper,

“Inference and Meaning,” Sellars introduced the notion of material rules of inference and explored their relationship with linguistic meaning (ch. 2, §2). In contrast to a formally valid inference, where the validity of an argument depends on its formal structure alone, materially valid inferences hold in virtue of the inferential connections between the (typically nonlogical) concepts that play a role in the premises and conclusions of arguments. Reasoning from ‘X is water’ to the conclusion that ‘X is a liquid’, or ‘X is something John can drink’, or ‘X is made of molecules’ are all materially valid inferences, whereas concluding that ‘My drinking X will increase the temperature on Saturn’, or ‘X would be a good fire-starter’ results in material invalidity.

I provide an overview of formalist thinking in ch. 1 by first discussing the relationship between logic and psychology during the nineteenth century, and then surveying several

5 formalist theories of reasoning that were developed afterward in the twentieth century. The discussion shifts from the psychology of reasoning and cognitive science to philosophy in ch. 2, where I discuss Sellarsian/Brandomian criticisms of formalism and introduce Brandom’s inferentialist theory of language. Mercier and Sperber’s interactionist theory of reasoning is discussed in ch. 3, and important connections between their view and Brandom’s are drawn.

Having drawn out their common theoretical ground, I then put forward my proposal to integrate the inferentialist view with the interactionist view. I conclude with a discussion of the implications of this hybrid view for some core debates in cognitive science, regarding the viability of the language of thought hypothesis, and the relationship between reasoning and modularity.

6 1 Formalist Approaches to Human Reasoning

§1 Introduction

Central to the revolution in modern logic brought about by Gottlob Frege and Bertrand

Russell in the late nineteenth and early twentieth centuries was a rejection of psychologism: the thesis that logical phenomena are psychological in nature—viz., that logic is a branch of psychology concerned with the nature of reasoning. This led most logicians to see logic and psychology as entirely separate disciplines. But at the same time, and in spite of this shift in intellectual culture, a number of theorists including George Boole, David Hilbert, Gerhard

Gentzen, and Alan Turing were putting forward ideas that would become a source of inspiration for psychologists who, in the sixties and seventies, were working towards reunifying psychology with logic.

§2-4 below provide a brief historical overview of psychology’s shaky relationship with logic from the advent of antipsychologism at the turn of the nineteenth century and up through the introduction of mental logic theories towards the end of the twentieth century. In terms of broad narrative structure, I will rely throughout on Luca Bonatti’s (1998) useful account of these developments. However, I will do so with an eye not just to how these ideas gave rise to mental logic theories in psychology (which, as a mental logic theorist, is Bonatti’s aim), but to formalist approaches to human reasoning more generally. The discussion in this chapter, then, will shift accordingly from formalist theories in the psychology of reasoning (§4 and §5) to the language

7 of thought hypothesis (§6), a dominant brand of formalism in both philosophy and cognitive science.

§2 The Rejection of Psychologism

As Bonatti points out, logicians did not turn away from psychology for reasons which would tell against logic-based theories of human reasoning per se. Rather, it was a more general opposition to idealist ways of thinking—a movement spearheaded by Frege and Russell—that led to the rejection of psychologism (1998: 12). Frege (1892/1997) distinguished between what he called “senses,” the objective, determinate meanings of linguistic expressions, and “ideas,” the subjective, “internal images” that we each associate with linguistic expressions. His concern was that if logical content were identical with the purely subjective psychological content of ideas, then no two individuals would ever entertain the same meanings, and hence there could be no contradictions, and so no communication and no science (1998: 11). But Frege sought only to establish that logical phenomena were not psychological in nature, not that psychological phenomena were not logical in nature:

The assertion both of what is false and of what is true takes place in accordance with psychological laws. A derivation from these and an explanation of a mental process that terminates in an assertion can never take the place of a proof of what is asserted. Could not logical laws also have played a part in this mental process? I do not want to dispute this, but when it is a question of truth possibility is not enough. For it is also possible that something not logical played a part in the process and deflected it from the truth. We can only decide this after we have discerned the laws of truth; but then we will probably be able to do without the derivation and explanation of the mental process if it is important to us to decide whether the assertion in which the process terminates is justified. In order to avoid this misunderstanding and to prevent the blurring of the boundary between psychology and logic, I assign to logic the task of discovering the laws of truth, not of assertion or thought. (1956: 290, emphasis added)

8 Frege’s point is that the rules of logic are not merely rules of reasoning; it doesn’t follow from this that reasoning is not governed by formal principles. This latter possibility is precisely what motivates formalist research programs in philosophy and psychology.

Russell (1914) was also concerned to refute idealism, and he aimed to do this by introducing a metaphysically robust doctrine of logical relations. Idealist metaphysics is based on Aristotelian logic, which holds that all propositions are of subject-predicate form. All relations, then, would be reducible to properties of objects. Moreover, there would be only one subject to which we could attach predicates, since, e.g., the proposition that ‘There are two subjects’ would not attach a predicate to a subject (1914/2008: 26). So, according to idealism, there is only one thing (the “Absolute”) and its properties, and there are no relations. Our common-sense conception of reality (according to which there are many entities standing in multifarious relations to one another) is therefore radically mistaken.

The problem here, Russell points out, is that not all relations are reducible to properties

(1914/2008: 32-36). Although, e.g., the symmetrical, transitive relation ‘Is a sibling of’ can be thought of as a property shared by siblings, asymmetrical relations such as ‘Is greater than’ cannot be construed in this way. If A is greater than B, then A has a greater magnitude than B.

But the difference between A and B is not reducible to their both simply possessing the property of being unequal to each other. This can be shown by simply inverting the relation; if it is now B that is greater than A, then this is again due to a difference in magnitude, but not the same difference. If it were the same difference, then A’s being greater than B would be indistinguishable from B’s being greater than A. Unless we want to say that the number five’s

9 being greater than the number one is the same relation as the number four’s being greater than the number one, we will have to admit the reality of asymmetrical relations.

§3 Rudiments of Formalist Thought

Despite its falling out of favor with most theorists, some logicians remained psychologistic in their thinking. Boole, for instance, conceived of logic as a “science of the intellectual powers” (1854: 4) and argued that theories of logic and probability

instruct us concerning the mode in which language and number serve as instrumental aids to the processes of reasoning; they reveal to us in some degree the connexion between different powers of our common intellect; they set before us what, in the two domains of demonstrative and of probable knowledge, are the essential standards of truth and correctness,—standards not derived from without, but deeply founded in the constitution of the human faculties. (1854: 2, emphasis added)

Hilbert (1925/1967) shared with Boole the view that human reasoning is an internal, rule- governed process of symbol manipulation, as well as the view that a formal-computational system in the mind is the source of our logical capacities. He argued that “as a condition for the use of logical inferences and the performance of logical operations, something must already be given to our faculty of representation, certain extra logical concrete objects that are intuitively present as immediate experience prior to all thought” (1925/1967: 376). This idea, that an innate formal-computational system lies behind human reasoning capacities, is present in all varieties of formalist theories.

Formalists differ, however, in their specifications of what, exactly, is innate in this system, and with respect to the dynamics between what is innate and what is acquired. Both mental logic theorists (whose views are discussed below in §4) and those who subscribe to the

10 language of thought hypothesis (discussed in §6 below), for instance, share the view that there is an innate mental syntax of thought, i.e., an array of simple and complex predicate formats, but language of thought theorists make the additional claim that content predicates are innate as well.

Before going into the details of the mental logic hypothesis, allow me to conclude this section with a brief discussion of the source materials out of which the mental logic model was developed.

Gentzen (1964) developed one of the first models of natural deduction. Unlike the axiom-based systems developed by Frege, Russell, and Hilbert, Gentzen’s formalization is based on deductive rules of inference. He aimed to develop a formal system that was just as logically rigorous as axiom-based systems but, unlike those models, psychologically realistic. This additional aim led him to contravene typical standards of theoretical parsimony by, e.g., introducing symbols and rules of inference for logical connectives, even when doing so results in logical redundancies. Formal inelegance is permissible here since, in ordinary reasoning, we do sometimes associate different meanings with logically equivalent expressions (1998: 17). For instance, (~P v Q) and (P → Q), although formally equivalent, do not strike us as two ways of making the same assertion. Psychological plausibility, for Gentzen’s purposes, was of higher theoretical value than formal elegance.

Gentzen’s theory of natural deduction was a breakthrough in the development of the idea that human reasoning processes are formal in nature. With this system, “the route from formal logic to natural reasoning was opened” (1998: 18), as it formalized logical deductions in such a way that they could be seen to run parallel to “actual reasoning” processes, i.e., the “forms of deduction used in practice in mathematical proof” (1964: 288). But it was Turing’s (1936) model

11 of computation that gave concrete plausibility to the idea that reasoning is syntax-driven. Turing showed how a particular kind of idealized machine, dubbed the “Turing machine” by Alonzo

Church (1937), could—by purely mechanical means—run any computational procedure which was algorithmically defined. A Turing machine consists of a machine head with a scanner, a machine table with a set of instructions (i.e., an algorithm to follow), and an infinitely long tape separated into squares containing symbols. The machine scans each square and computes the values of functions according to the instructions provided in its machine table. For example, the device can implement the following algorithm:

If the current square contains a ‘0’, leave it alone and then move one square on the left. If the now current square contains a ‘1’, erase that symbol, replace it with a ‘0’, and then move one square to the right.

These instructions can be followed repeatedly until all of the squares contain a ‘1’.

The significance of Turing’s account is that it showed how an entirely mechanical device could perform computations correctly, and through the use of syntactical rules alone. This lent plausibility to the idea that human reasoning is an internal process of symbol manipulation according to syntactical rules, as it proved that purely mechanical, syntax-driven reasoning can produce the right kinds of outputs without the aid of informal judgment. Before Turing’s theory of computation, there was no explanation of how rational thinking, as conceived by the formalist, i.e., as the formally valid transition from one thought to another, was possible. Jerry Fodor puts the point nicely,

“What determines the logical form of a thought?” and “How does the logical form of a thought determine its causal powers?” Answer: The logical form of a thought supervenes on the syntax of the corresponding mental representation, and the logical form of a thought determines its causal powers because the syntax of a mental representation determines its computational role, as per the operations of Turing machines. So we can now (maybe) explain how thinking could be both rational and mechanical. Thinking can be rational because syntactically specified

12 operations can be truth preserving insofar as they reconstruct relations of logical form; thinking can be mechanical because Turing machines are machines. (2001: 19)

With the contributions of Boole, Hilbert, Gentzen, and Turing, the motivations for a formalist approach to human reasoning were in place. The next section is concerned with the most explicitly logic-centered variant of formalism: mental logic theory. In the sections following that, we’ll see two additional theories that fall underneath the formalist paradigm: dual process theory in the psychology of reasoning (§5) and the language of thought hypothesis in the philosophy of mind and cognitive science (§6).

§4 Mental Logic Theory

Mental logic models of reasoning (Braine 1978; Braine and O’Brien 1998; Rips 1983,

1994) propose sets of mental inference rules in order to explain our deductive reasoning capacities. These systems operate with “natural connectives” such as AND, OR, and ‘/’ which are the psychological analogs of the standard logic operators ‘&’, ‘v’, and ‘→’. The differences between mental logic systems and standard logical systems (discussed below) are the result of two methodological constraints which aim to ensure psychological plausibility: the meanings of natural connectives such as AND and OR should align with the meanings of their natural language analogs ‘and’ and ‘or’ (1978: 9), and we should not propose as rules of inference schemata that are never used in actual reasoning (1978: 14). Braine and O’Brien (1998) refer to the latter constraint as “psychological validity” (49), and list three further properties of mental logic schemata: they are elementary, which is to say that they each correspond to what would be a

13 single step in an instance of deductive reasoning, they are primitive, meaning early to develop in reasoners, and universal, i.e., identical across cultures.

Mental logic theorists do not claim to tell the whole story about reasoning:

Mental logic is deeply embedded within a pragmatically motivated architecture, and inferences are regularly drawn from information that includes knowledge retrieved from long-term memory, beliefs, opinions, guesses, and various kinds of implicatures. Logical inferences reside comfortably in a line of reasoning with analogical, causal, pragmatic, and probabilistic ones. (Braine and O’Brien, 1998: 47)

Clearly, not all mental transformations are deductive ones, and we need to leave room for obviously nondeductive transformations that can occur in image manipulation, in forgetting, and in various sorts of inductive and analogical inference. (Rips, 1994: 11)

They aim rather to provide explanations of the specifically logical component of reasoning.

Braine (1978), who was the first to propose MLH as a substantive psychological theory, put forward a list of mental inference rule schemata N1-N18 to serve as the basis for a model of propositional reasoning. N1-N18 are claimed to be logically valid, psychologically elementary, and to comprise a complete list of the elementary steps of deductive reasoning (15).2

Braine’s schemata differ from Gentzen’s in significant ways. For example, AND (N1 and

N2) and OR (N3 and N4) have a coordinate structure: P1, P2, and P3, e.g., can be rendered as P1

AND P2 AND P3, or as P1 OR P2 OR P3. Braine opts for coordinate rather than binary structure, as in Gentzen’s system, in order to respect the meanings of ‘and’ and ‘or’ in natural language, which are not, as in standard logic, binary connectives (1978: 9-10). Also noteworthy in Braine’s system is the absence of the truth-functional conditional, which he replaces with an inference line theory: if-then statements take the form P/Q, where ‘/’ merely indicates that, if P is known to

2 Braine notes that a system of standard logic can be formulated out of his mental logic by making the following changes: “First and most important, one makes the truth conditions of the inference line explicit by reconstruing it purely as a connective, the truth-functional conditional. Having thus eliminated its function as an inference rule, one introduces a special schema, Modus Ponens, to allow detachment of the second clause. A second move is to eliminate the vagueness of OR by legislating the inclusive sense. One then simplifies the overall system by assigning AND and OR a binary rather than coordinate structure, by allowing NEG to apply freely to compound propositions, and by pruning many redundant schemata (1978: 18).

14 be true, Q may be inferred (1978: 8). Modus ponens (MP) and modus tollens (MT) are also absent; MP inferences follow from the definition of the inference line, and no inference rule for

MT is given since MT inferences are not elementary (1978: 15). There are a number of other differences between Braine’s and Gentzen’s systems, but the important point is that Braine’s system is designed to mirror “actual reasoning” processes more closely than does Gentzen’s. Ex falso quodlibet, e.g., is also absent, because we are not, in ordinary reasoning, inclined to infer any proposition whatsoever from a contradiction.

Braine emphasizes that these mental inference rules are not introspectively accessible

(1978: 16). This affords a possible explanation of our incompetence with regard to formal reasoning: although we use mental inference rules in order to engage in deductive reasoning, we are not aware of the logical consequences of our inferences, since such awareness requires working out the “minimum commitments” of major premises used in reasoning. Ordinary reasoners, unlike logicians, do not have the requisite training to carry out such a task. But the products of deductive reasoning are introspectively accessible, and so reportable, and thus available for empirical study. Accordingly, mental logic theories proceed by examining these outcomes and formulating hypotheses about the mental machinery behind their production.

Note that the primary motivation for positing a mental logic is to explain rational behavior:

We have argued that one reason the mental logic evolved was to serve the practical goal of integrating information coming in at different times or from different sources, drawing inferences that go beyond the information as given (Braine, 1990; O’Brien, 1993). For instance, one learns P or Q from one source and not Q from another: an intelligent being needs some mental mechanism that will integrate these pieces of information by inferring P; the mental logic satisfies the need. (Braine and O’Brien, 1998: 47)

15 The mere fact that we exhibit such behavior, however, underdetermines the nature of the underlying cognitive processes. Some cognitive scientists reject the idea that rules of inference play any role at all in reasoning. Philip Johnson-Laird (1980), for example, argues that reasoning is more akin to the testing of “mental models,” whereby we construct mental representations of premises and conclusions and reject inferences for which counterexamples come to mind (i.e., models in which the premises of an argument are true, and its conclusion is false). I will present, in ch. 2, a theory of reasoning according to which rules of inference are central, but not the ones postulated by mental logic theorists. On that alternative theory, material, rather than formal rules of inference are central to human reasoning.

Mental logic models are formalist theories of human reasoning par excellence. They explain the capacity to reason deductively by positing internal symbols and innate formal rules of inference with which to manipulate them. The next section discusses dual process theory, an account of reasoning which does not necessitate a commitment to an inner logic. It is, however, committed to a formalist conception of rationality. Indeed, Kahneman’s book, which is at the center of the discussion that follows, is premised on the idea that reasoning is problematically biased, and that these biases are due to the nature of the human mind.

§5 Dual Process Theory

Starting in the late 1960s, Daniel Kahneman and Amos Tversky began overturning the social scientific paradigm for theorizing about rationality. Their research on cognitive biases revealed that human beings are systematically prone to (what Kahneman and Tversky

16 characterized as) irrational thinking. In his popular book, Thinking Fast and Slow (2011),

Kahneman describes the social science scene at the time,

Social scientists in the 1970s broadly accepted two ideas about human nature. First, people are generally rational, and their thinking is normally sound. Second, emotions such as fear, affection, and hatred explain most of the occasions on which people depart from rationality. Our article challenged both assumptions without discussing them directly. We documented systematic errors in the thinking of normal people, and we traced these errors to the design of the machinery of cognition rather than to the corruption of thought by emotion. (2011: 8)

Whereas emotion had been taken to be the source of irrationality, Kahneman and Tversky’s research is widely taken to have revealed that the cognitive mind itself can be the source of irrationality as well. Kahneman (2011) develops a theory of cognition that aims to make sense of the irrational tendencies of the human mind.

Kahneman’s dual process theory (DPT) groups cognitive processes under two headings

(2011: 20-24). Fast, automatic processes of monitoring, recognition, and association go under the heading of System 1, which is in charge of tasks such as regulating routine bodily movements, monitoring one’s environment, comprehending simple sentences, and alerting us to the out-of-the-ordinary. We perform these tasks without any experience of mental exertion.

System 2 is in charge of tasks that require sustained effort and concentration, such as performing mathematical computations and merging onto a busy highway. When System 1 detects a surprising change in the environment or has difficulties implementing its regular tasks, it alerts

System 2. System 1 is fast and intuitive. System 2 is slow and (sometimes) rational, in a sense that we will examine shortly.

Association is the key cognitive mechanism involved in System 1 thinking. Exposure to ideas, whether in the form of words or behaviors, triggers associative connections between ideas that are stored in long-term memory. Psychologists study these associative processes by

17 measuring the priming effects of ideas on behavior (2011: 52-58; see also Kouider and Dehaene,

2007). For example, presenting two groups of subjects with arbitrary numbers and then asking them a question that requires estimating a numerical quantity will affect the value of the estimates they go on to give (2011: 122-123). Presenting subjects with a lower value primes them to give lower estimates, while presenting them with a higher value has the opposite effect.

This priming effect, known as “anchoring,” demonstrates how System 1 processes information.

No matter how irrelevant the information contained in the prime is to answering a question,

System 1 will retrieve that information and use it to make an estimate. System 1 is oblivious to the rational connections, or lack thereof, between pieces of information. It thinks in associative terms, and as studies inducing the anchoring effect show, it is easily given to suggestion.

Kahneman describes the characters of System 1 and System 2 as follows,

In the unlikely event of this book being made into a film, System 2 would be a supporting character who believes herself to be the hero. The defining feature of System 2, in this story, is that its operations are effortful, and one of its main characteristics is laziness, a reluctance to invest more effort than is strictly necessary. As a consequence, the thoughts and actions that System 2 believes it has chosen are often guided by the figure at the center of the story, System 1. (2011: 1)

Another psychological phenomenon that implicates System 1 in irrational thinking is known as “cognitive ease” (2011: 59-70). System 1 is constantly monitoring aspects of your experience, such as whether any important changes are occurring, whether any of those changes constitute a threat, whether a task is being handled properly, and so on. When you are not encountering problems in any of those areas, you are in a state of cognitive ease. You are in such a state when you are in a good mood or familiar with the task at hand. Cognitive ease and its opposite, cognitive strain, are often used by System 2 as criteria for judgments of truth and falsehood (2011: 62). While System 2 is trying to determine whether a statement is true or false,

18 System 1 will measure the statement’s degree of familiarity. If the statement seems familiar, the mind enters a state of cognitive ease, and System 2 becomes more likely to judge that the statement is true. If, on the other hand, the statement is unfamiliar, then System 2 becomes more likely to judge that the statement is false. But how familiar you are with a statement tells you nothing about the likelihood of its truth or falsity. It is simply the fact that familiar information is more easily processed by System 1 than unfamiliar information that inclines System 2 to rely on these feelings of cognitive ease and cognitive strain in making judgments. System 2, then, is also to blame for irrational thinking.

Several studies demonstrate System 2’s laziness (2011: 44-46). For instance, Shane

Frederick (2005) gave subjects the following information: a bat and a ball have a combined value of $1.10, and the bat is worth $1 more than the ball. He then asked the subjects how much the ball is worth. System 1 immediately suggests that the answer is 10¢ because a ¢10 ball plus a $1 bat totals to $1.10. But if the ball costs ¢10, and the bat costs one dollar more than ¢10, then their combined value would be $1.20. So, the intuitive answer is false. As it turns out, “more than

50% of students at Harvard, MIT, and Princeton gave the intuitive—incorrect—answer. At less selective universities, the rate of demonstrable failure…was in excess of 80%” (2011: 45).

Anecdotally, Kahneman mentions another study in which college students were given the following syllogism, and asked to determine whether it was valid:

All roses are flowers. Some flowers fade quickly. Therefore some roses fade quickly.

A “large majority” of the students endorsed the syllogism as valid. It is not valid, of course, because it could be that none of the flowers that fade quickly are roses. Determining whether or

19 not the premises entail the conclusion requires System 2 processing, since System 1 is only capable of associative processing, and incapable of contemplating logical possibilities. But since

System 2 is too lazy to do its job, it opts for the intuition delivered by System 1 that the syllogism is valid. ‘Roses’ is associated with ‘flowers’, then ‘flowers’ with ‘fading quickly’, and then ‘roses’ with ‘fading quickly’. The associative connections made the validity of the argument seem so obvious that the majority of the students did not bother to check whether or not they were logical. Here is Kahneman’s take on the results:

“Lazy” is a harsh judgment about the self-monitoring of these young people and their System 2, but it does not seem to be unfair. Those who avoid the sin of intellectual sloth could be called “engaged.” They are more alert, more intellectually active, less willing to be satisfied with superficially attractive answers, more skeptical about their intuitions. The psychologist Keith Stanovich would call them more rational. (2011: 46)

Kahneman is working with a formalist conception of rationality, according to which the function of reasoning is to perform logical and probabilistic computations in order to arrive at truths. On this approach, studies like those of Frederick’s and Kahneman’s seem to indicate that reasoning typically fails to perform its function. This leaves us with the following picture of reasoning:

System 2 is in charge of formal processing, but quite often fails to arrive at rationally consistent

—formally valid—conclusions; this is due to both to the cognitive biases of System 1, and to the inherent laziness of System 2 that leads to it rely on System 1’s biased suggestions. Cognitive scientists working within the formalist paradigm have taken this to show that human beings are, for the most part, irrational.

One important point of divergence between DPT and interactionism—to be discussed in ch. 3—concerns their opposing accounts of intuition. Kahneman conceives of intuition as fast, automatic, and non-rational, while reasoning is slow, deliberate, and sometimes (perhaps rarely) rational. In contrast to this account of intuition and reasoning as distinct cognitive processes,

20 Mercier and Sperber argue that reasoning is itself a process of intuitive inference. Again I leave the details to ch. 3.

We’ve now seen how two theories in psychology exemplify the formalist approach to reasoning. MLH seeks to account for the capacity to draw rational, i.e., logically valid, inferences by postulating mental inference rules. DPT does not postulate a mental logic but presents a picture of cognition according to which thought processes are either automatic and associative (System 1) or conscious and formal (System 2). System 1 is incapable of rational thinking, and although System 2 can engage in formal reasoning, it is often too lazy to do so.

The formalist depiction of reasoning is, of course, an affront to human nature qua rational animal. One of the primary aims of this essay is to present an alternative account of reasoning— one in which formal reasoning is not front and center, but derivative from a more basic kind of reasoning. The sense in which it is derivative will be made clear by the discussion in ch. 2 (§3.1) of Brandom’s logical expressivism. We turn now in this last section to the language of thought hypothesis, the most popular formalist approach in the philosophy of mind and cognitive science.

§6 The Language of Thought Hypothesis

Fodor (1975, 1987) argues that we reason in an internal, formal language: “the language of thought,” or “Mentalese.” The language of thought hypothesis (LOTH) is a species of the representational theory of mind, according to which propositional attitudes such as beliefs, desires, hopes, fears, etc. are relations between subjects and their mental representations. What’s distinctive of LOTH is a claim about the nature of propositional attitudes: not only are the

21 objects of propositional attitudes syntactically structured—e.g., the belief that The Earth goes around the Sun has four components: ‘The Earth’, ‘The Sun’, ‘goes’, and the ‘around’ relation— but mental states themselves have constituent structure. In other words, believing, desiring, hoping, and fearing transpire in a language of thought (“Mentalese”). The reason that Mentalese is a language, on Fodor’s view, is that it has two structural features which are possessed by all languages: a combinatorial syntax, and a combinatorial semantics.

The sentence ‘The Earth is 93 million miles from the Sun’ has two atomic constituents:

‘The Earth’ and ‘the Sun’, and one compound constituent ’93 million miles’, which itself has the atomic constituents ’93’, ‘million’, and ‘mile’. A language with a combinatorial syntax has syntactically structured representations with atomic and compound constituents, and its compound constituents are themselves made up of atomic components. Switching the positions of ‘Earth’ and ‘Sun’ in ‘The Earth goes around the Sun’ changes the meaning of the sentence—its semantic content is a function of its syntactical structure together with the content of its constituents. LOTH is the claim that we think in Mentalese and that Mentalese sentences, i.e., propositional attitudes, are syntactically structured and semantically determined in the manner described above.

LOTH theorists cite the productivity and systematicity of natural language production and comprehension as evidence that thought, in general, is productive and systematic (Fodor and

Pylyshyn 1988). The productivity of linguistic capacities refers to the apparent boundless nature of the sentences that we can produce and understand (see Chomsky 1972). Since there seems not to be any limit, in principle, on the number of sentences that we can formulate and understand, then there would also seem to be no limit, in principle, on the number of thoughts that we can

22 entertain. So, our representational system must itself be productive, i.e., we must think in a language with the kind of combinatorial structure mentioned above.

Fodor and Pylyshyn acknowledge that their productivity argument is controversial, since it requires an idealization—we only ever actually think a finite number of thoughts—but they view this as trivial and irrelevant to the question of whether we could, given an infinite amount of time, entertain an infinite number of thoughts (1998: 34). At any rate, they have what they take to be a much stronger argument for LOTH anyhow—the argument from systematicity, which goes like this: If a sentence such as ‘Smith married Juarez’ is intelligible to a language- user, then so too is the sentence ‘Juarez married Smith’, and in order for those sentences to be intelligible to subjects, they must capable of entertaining them as thoughts, so thought, too, must be systematic.

§7 Conclusion

LOTH theorists view reasoning as a syntax-driven process: rational thinking is a function from the syntactical structures of sentences in Mentalese together with the semantic content of the atomic and compound constituents of those sentences. In other words, thoughts are mental representations, and the mental processes which transform those representations are governed by formal rules which are truth-preserving. Many objections to LOTH have been raised, most notably by connectionists (Bechtel and Abrahamsen 1990, Churchland 1995). But the critique of formalism that I introduce in ch. 2 and go on to strengthen in ch. 3 will implicate LOTH simply in light of its commitment to a formalist view of reasoning, and independently of any of its

23 particular formalist commitments. If the LOTH model of reasoning is based on formal deduction and reasoning turns out not to be anything like formal deduction, then the plausibility of LOTH is very much in question. The same point applies to MLH––both theories are premised on the assumption that there is something akin to a formal logic in the brain, and that an account of this formal-computational system is the key to explaining rational inference.3

In the next chapter, I will rehearse arguments from Sellars (1953/2007) and Brandom

(1994) in order to begin building a case against this formalist assumption. We’ll see there that there are strong reasons to doubt that formal inference is the correct paradigm of human reasoning. In ch. 3, I will strengthen this case by showing how the Sellarsian/Brandomian view of reasoning is vindicated by recent work in cognitive science—particularly by the

“interactionist” model of reasoning championed by Mercier and Sperber (2017). I will first draw attention to the fundamental theoretical commitments that Brandom’s inferentialist theory of meaning shares with the interactionist theory of reasoning. I’ll then show how what is lacking in each can be provided by the other. Interactionism provides an empirical framework for inferentialism, and inferentialism provides a conceptual framework for interactionism. My aims, then, are twofold: first, to build a case against formalism by presenting counterarguments from inferentialism and interactionism; second, to point towards new theoretical territory that I believe inferentialism and interactionism, seemingly unknowingly, both occupy.

3 See Braine and O’Brien, 1998: 47-49 for clarification on the similarities and differences between MLH and LOTH.

24 Ch. 2 Inferential Materialism and Logical Expressivism

§1 Introduction

My aim in ch. 1 was to introduce formalism by surveying a number of such approaches in disciplines concerned with the study of reasoning: mental logic theory and dual process theory in the psychology of reasoning and the language of thought hypothesis in the philosophy of mind and cognitive science. Two general formalist theses run throughout these views: (i) that the brain comes equipped with logical machinery and (ii) that we can explain the nature of reasoning and rationality by way of an account of that logical machinery. We resume the discussion of formalism in this chapter, but now with a critical eye. Additionally, there will be a shift in our theoretical context: from psychology and cognitive science to the philosophy of language and the philosophy of logic. We make this shift in order to bring the formalist approach to rationality

(which comes part and parcel with the formalist approach to reasoning) into view and to contrast it with the alternative position that Sellars and Brandom provide. We’ll then have before us two starkly opposed views, between which we can adjudicate—one of the main tasks of ch. 3.

Both Sellars and Brandom reject a brand of formalism which is dominant in philosophy.

Brandom characterizes that view as follows:

Often…inferential articulation is identified with logical articulation. Material inferences are then treated as a derivative category. The idea is that being rational—mastering proprieties of inference and so being subject to the force of the better reason—can be understood as a purely logical capacity. (1994: 98, emphasis in original)

According to this line of thought, wherever an inference is endorsed, it is because of belief in a conditional. Then the instanced inference is understood as implicitly involving the conditional

25 "If it is raining, then the streets will be wet." With that "suppressed" premise supplied, the inference is an instance of the formally valid scheme of conditional detachment. The "dogma" expresses a commitment to an order of explanation that treats all inferences as good or bad solely in virtue of their form, with the contents of the claims they involve mattering only for the truth of the (implicit) premises. According to this way of setting things out, there is no such thing as material inference. This view––which understands "good inference" to mean "formally valid inference," postulating implicit premises as needed––might be called a formalist approach to inference. (1994: 98, emphasis in original)

The notion of material inference plays a key role in both Sellars’ and Brandom’s arguments against formalism. It will be best, then, to get clear on the distinction between formal and material inference at the outset. Formally valid inferences are so in virtue of the form or structure of their premises and conclusions. Materially valid inferences, by contrast, are content- based. They are “the kind of inference whose correctnesses essentially involve the conceptual contents of its premises and conclusions may be called, following Sellars, “material inference” (1994: 97, emphasis in original). Brandom provides the following examples:

Pittsburgh is to the West of Philadelphia, so Philadelphia is to the East of Pittsburgh. Today is Wednesday, so tomorrow will be Thursday. Lightning is seen now, so thunder will be heard soon (1994: 97-98).

These inferences lack a formally valid structure, but everyone—including the formalists—agrees that they are good inferences nonetheless, in some sense. The disagreement between those who subscribe to formalism about inference and those who, like Sellars and Brandom, recognize material rules of inference as a source of rational authority in their own right, concerns the explanation of this particular kind of correctness.

On the Sellarsian/Brandomian view, the abovementioned inferences do not have a

“hidden structure.” Rather, they are licensed by material rules of inference, which both constitute the meanings and govern the use of the expressions/concepts WEST, EAST, TODAY,

TOMORROW, WEDNESDAY, and so on. The formalist, on the other hand, takes these inferences to

26 be enthymemes: their true—formally valid—structure is “hidden.” ‘Philadelphia is to the East of

Pittsburgh’ follows from ‘Pittsburgh is to the West of Philadelphia’ because anyone who draws that inference, according to the formalist, relies on the additional, “hidden” premise: ‘Whenever something X is to the east of Y, Y is to the West of X’. Material inferences, on the formalist approach, are just instances of conditional detachment. In other words, there are no material inferences; all “good” inferences are rational in virtue of their logical form. In the case of so- called material inferences, that form is simply hidden.

So, formalists explain away the goodness of material inferences in terms of formal validity. As we’ll see in the next section, Sellars argues forcefully against this position. Brandom

(§3.1 and §3.2) goes further in not only rejecting that order of explanation but inverting it. He argues that the goodness of formally valid inferences is explained by the goodness of materially valid inferences.

§2 Sellars on Material Rules of Inference

As the reign of logical positivism came to an end in the latter half of the 20th century, philosophers began thinking differently about semantics. W.V. Quine (1951) famously argued against the semantic atomism underpinning the verificationist theory of meaning. The positivists held that the meanings of statements consist of the observations which would either confirm or disconfirm their factual significance. What Quine pointed out was that a set of observations only confirms a statement within the context of an entire belief system. As an empiricist, Quine does not reject verificationism outright but points out that the view is only serviceable when combined

27 with a commitment to confirmation holism. The combination of verificationism with confirmation holism led Quine to adopt a more general notion of semantic holism, according to which the semantic properties of words and sentences depend not only on the sensory inputs that tend to trigger their production but also on their myriad inferential connections with other linguistic expressions. A version of this semantic theory was also developed, though on substantially different grounds, by Quine’s contemporary, Wilfrid Sellars, to whose views we now turn.

Sellars (1953/2007) argues that material rules of inference govern linguistic usage with an authority which is independent of that of formal rules of inference. He aims to demonstrate this by showing that formal rules are ill-suited for the treatment of subjunctive conditionals, which serve a crucial function in natural languages: the expression of material rules of inference.

Additionally, Sellars rejects the theory that meanings are determined by two distinct kinds of rules: syntactical rules which govern the manipulation of expressions, and semantic rules, the following of which confers meaning onto descriptive terms. On Sellars’ alternative view, the meanings of descriptive terms are wholly determined by material transformation rules.

The material validity of inferences depends essentially on the conceptual contents contained in their premises and conclusions, rather than on their formal structure. Sellars’ case in point is the inference from ‘It’s raining’ to ‘The streets will be wet’ (1953/2007: 3). As noted above, formalists take this to be an enthymeme; once the suppressed premise ‘Whenever it rains the streets will be wet’ is made explicit, the argument becomes formally valid, and this is what makes the inference a good one. Sellars opposes this line of argument. He argues that even with the “enthymematic” premise supplied, the validity of the subjunctive formulation of that

28 inference issues from material, rather than logical rules of inference. And since we make valuable and arguably ineliminable use of subjunctive conditionals in both ordinary and scientific discourse, Sellars rejects the formalist view as an inadequate model of reasoning.

Here is the subjunctive formulation:

(S1) Since every time it rains the streets are wet, if it were to rain the streets would be wet.

We would expect this inference to be licensed by the following logical principle:

(LP) For all x, if φx implies Ψx, then φa implies Ψa.

But here, Sellars notes, a problem arises (1953/2007: 13-14), because the subjunctive conditionals that (LP) licenses would be of the form:

If φx implies Ψx were the case, then it would be the case that φa implies Ψa.

So, the inference which would be licensed by (LP) is

(S2) Since every time it rains the streets are in point of fact wet, it will rain implies that the streets will be wet.

The problem for the formalist is how to interpret the ‘since’-clause. If it’s taken to express a material implication—it’s never the case both that it rains and the streets are not wet—then one would not be inferring, on the basis of (LP), Wet Streets from Rain, but simply drawing out a material implication:

~(Rain & ~Wet Streets), so Rain → Wet Streets.

Furthermore, Sellars points out, we aren’t inclined to draw the subjunctive inference from Rain to Wet Streets on the basis of the mere fact that Rain and Wet Streets always come together

(1953/2007: 14). We recognize the inference as a good one because it is part of the meaning of

‘rain’ that rain tends to wet whatever it comes into contact with, and because it is part of the

29 meaning of ‘street’ that streets tend to get wet when it rains. We also recognize that Rain does not imply Wet Streets for any streets that are underneath a bridge (but then not if there are strong wind gusts, or if someone under the bridge is using a hose). Materially valid inferences are not monotonic—they are counterfactually robust.4

We’ve seen that the formalist cannot give an account of the validity of (S1) by interpreting the since clause as the expression of a material implication. Perhaps, then, it expresses an entailment (1953/2007: 14):

(S3) Since rain entails wet streets, it will rain entails that the streets will be wet.

(LP) does license this inference, and Wet Streets is being inferred from Rain (which is the subjunctive inference one wants to draw from Rain), but in order to make this move, Sellars points out, one has to introduce a material rule of inference:

To say that rain entails wet streets is to convey exactly the same information as to say that a sentence asserting the existence of wet streets may be inferred from a sentence asserting the existence of rain. Thus our ultimate purpose of explaining the original subjunctive conditional without appealing to a material rule of inference would not have been achieved. (1953/2007: 14, emphasis in original)

Sellars tries one last formulation (1953/2007: 15):

(S4) If it were the case both that every time it rains, the streets are wet and that it is raining, then the streets would be wet.

Here, the enthymematic premise can no longer be expressed as a ‘since’-clause, because the antecedent of this conditional contains an assertion: if it were the case that P → Q, and P is true,

4 Formal inferences are monotonic. If (P → Q) is valid, then (P & R → Q) is valid, and so are (P & R & S → Q) and (P & R & S & T → Q), and so on—no addition of further propositions to the antecedent of a valid sequent will render it invalid. If we add to the antecedent of the current formalist rendition of our conditional the proposition that ‘Everywhere the streets are enclosed by steel structures’ then it would still be logically valid to draw the inference that Rain implies Wet Streets. We’ll see in the next section that, on Brandom’s expressivist view of logic, this inference only counts as a logically valid one if we privilege the conceptual contents of the logical terms over that of the descriptive terms. Logical vocabulary, contra formalism, isn’t privileged by nature.

30 then Q would be true. This formulation, then, does not express a subjunctive inference. Sellars concedes that (S4) seems, at a glance, to capture what (S1) expresses, but fails to do so for a significant reason:

It is sufficient to point out that on this interpretation all such subjunctive conditionals would be true! Surely some sentences of the form “If a were φ, a would be Ψ” are false, in other words some sentences of the form “Even though a were φ, it need not be Ψ” are true. But on the theory under examination, the former, when explicated turns out to be a logical truth, and the latter a contradiction. (1953/2007: 15, emphasis in original)

By demonstrating the inadequacies of formulations (S2)-(S4), Sellars takes himself to have shown that material rules of inference have a claim to rational authority which is independent of that of formal rules of inference, which is to say that they are essential to the languages that we speak—subjunctive conditionals are the expressions of material rules of inference, and their use in natural language is widespread and frequent. The next stage in Sellars’ argument is to show that material rules of inference are not only essential to the languages that we speak—those that happen to make use of subjunctive conditionals—but to any language that contains descriptive terms.

Building on Kant’s idea that formal rules of inference are essential for the possibility of language, concept-use, and thought, Sellars argues that material rules of inference are likewise essential to meaning.5 Kant’s idea is that one cannot simply reason with, e.g., the stand-alone concept DOG, as Hume might have imagined. Learning the concept DOG requires coming to see how it functions in judgments such as ‘Dogs are animals’, 'Dogs are domesticated’, and so on.

Concepts occur essentially in judgments. Furthermore, to understand the judgment ‘Dogs are animals’, one needs to understand how that judgment relates to others, e.g., ‘Dogs are mammals’,

5 Both Sellars’ and Brandom’s readings of Kant are discussed in this chapter for expository purposes. Whether those interpretations are faithful to Kant’s actual views is a matter which is outside the scope of this essay.

31 and ‘Mammals are animals’. It is this point that motivates Kant to pick out formal rules of inference as the wellspring of linguistic meaning, as understanding that ‘Dogs are animals’ requires understanding the syllogism ‘All dogs are mammals. All mammals are animals.

Therefore, all dogs are animals’, which is merely an instance of the formal schema ‘All A are B.

All B are C. Therefore, all A are C’. So, on this view, in order to acquire meanings, all one needs is a basic grasp of formal rules of inference, and concepts (derived from sensory experience) to which those formal rules can be applied.

Sellars argues that what is missing from this picture is the meaning-constituting role of material rules of inference. He rejects the claim that the meanings of words like ‘red’ are learned by associating the sound /red/ with red things in one’s environment (or, for that matter, in one’s

“realm of sense-data”). To bring out this point, Sellars (1953/2007: 23) asks us to consider the following sentences:

In Schmidt’s language, ‘rot’ means red. In Schmidt’s language, ‘und’ means and.

From the perspective he seeks to overturn, it appears that each sentence concerns a different kind of meaning. “‘Rot’ means red” asserts a psychological fact about how German speakers respond to red things, while “‘und’ means and” asserts a grammatical fact about the use of ‘und’ in

German and the use of ‘and’ in English. But Sellars argues that this is a mistake, and makes the following far-reaching claim: The ‘means’ in both (1) and (2) expresses facts about the rule- governed usage of words in German and English. Specifically, it conveys that the material rules of inference governing the uses of ‘rot’ and ‘und’ amongst German speakers are the same (or relevantly similar) to the ones that govern the uses of ‘red’ and ‘and’ amongst their English

32 counterparts. The meanings of descriptive terms, on Sellars’ view, are as much determined by material rules of inference as are the meanings of logical terms by formal rules.

It follows on this account that basic material inferences, such as the one expressed by

‘My car is running, so it will move if I press the gas pedal’, are not merely psychological habits of association but genuine acts of reason. And while the formalist would insist that there is a logical structure underlying such inferences, e.g., ‘My car is running. All running cars move when their gas pedals are pressed. Therefore my running car will move when I press the gas pedal’, Sellars argues that the original formulation is materially valid as it stands, in virtue of the material inferential relations that hold between the concepts RUNNING CAR, GAS PEDAL, and others.

So, there are material in addition to formal rules of inference. But what, in general, is a

“rule of inference”? Sellars argues that any plausible definition of a rule must both “have the normative flavor characteristic of ‘ought,’ or ‘ought not’ or ‘may’ or ‘may not’ and take into account the fact that all rules are rules for actions” (1953/2007: 18).6 A rule does not entail merely that one can or cannot do something, but that one is permitted or not permitted to do something. A rule of inference, in the most basic sense, is a rule of conditional assertion: it permits one, in light of having made one assertion, to make or not make certain others. In the case of a valid inference, the assertion of one proposition warrants the assertion of a further proposition to which it is inferentially related. Invalid inferences lack such connections.

6 “Ought-to-be” rules imply “ought-to-do” rules (Sellars, 1969/2007). Ought-to-be rules take the form “Xs ought to be in state φ, whenever such and such is the case.” Ought-to-do rules take the form “If one is in C, one ought to do A,” where ‘C’ denotes a circumstance and ‘A’ the action to be carried out when that circumstance obtains.

33 Sellars’ views on material rules of inference were taken up and further developed by

Robert Brandom, to whom we turn in the next section. Like Sellars, Brandom is an “inferential role semanticist” in that he identifies the meanings of expressions with their roles in reasoning, and thereby explains semantic content in terms of linguistic use. The sort of linguistic use relevant to explaining semantic content, according to the inferentialist, is that which occurs in social practices with a particular discursive structure: ones in which participants make assertions, whereby they commit themselves to claims, which in turn entitles them to make certain further, materially inferentially related claims, and disbars them from making certain others—those which are materially incompatible.

We’ll return to this normative-pragmatic element of Brandom’s inferentialism in ch. 3 in connection with Mercier and Sperber’s interactionist theory of reasoning. The discussion for the remainder of this chapter is focused on Brandom’s critique of formalism, along with his philosophy of logic and his theory of meaning: logical expressivism and semantic inferentialism.

§3.1 Logical Expressivism

Brandom finds in Sellars’ work resources for an expressivist conception of logic, according to which logical vocabulary is a relatively late addition to an already up and running social practice of giving and asking for reasons, rather than being a conceptual precondition for the existence and rationality of that practice.7 On Brandom's reading, the main takeaway from

Sellars’ discussion of subjunctive conditionals is “not the indispensability of the vocabulary of

7 Brandom’s expressivism is also heavily influenced by Frege and Dummett (Brandom, 1994: 107-30).

34 conditionals that permit detachment inferences even with counterfactual premises”; rather, “it is the indispensability of what those conditionals express: the implicit proprieties of material inference that they help make explicit” (1994: 103). The function of logical vocabulary, according to Brandom, is to make explicit the implicit material inferential relations between the concepts employed in ordinary and scientific discourse. For example, by virtue of the ‘all’ and the ‘are’ of the categorical sentence ‘All planets are astronomical objects’. one can use that sentence to express a material inferential relation implicit in the ordinary material inference

‘Earth is a planet, so Earth is an astronomical object’.

Sellars’ argument shows that we cannot understand material validity in terms of formal validity. It also shows that neither the formal validity of arguments containing nonlogical terms nor the capacity to associate nonlogical terms with external stimuli is sufficient to account for the meanings of nonlogical terms. But, Brandom claims, the converse is the case. We can explain formal validity in terms of material validity. And meanings in general—including, as a special case, the meanings of logical terms—can be understood in terms of the material inferential roles that concepts play in reasoning.

Following Frege, Brandom understands the nature of good inference in terms of invariance under substitution—showing that an argument is good in virtue of its logical form alone presupposes a method of dividing the content of that argument into that which is held fixed, and that which is variable (1994: 104). By holding the specifically logical terms of an argument fixed, and varying the nonlogical terms, we can show that an argument is good solely in virtue of its logical form, in abstraction from any nonlogical content that it might have. But, as Brandom points out, this substitutional method is generalizable; we can privilege any

35 vocabulary we please (call it K-vocabulary) and thereby show that an argument is good in virtue of its K-form. If we hold the K-vocabulary of an argument fixed, and in varying the non-K vocabulary, we produce no materially incorrect inferences, then that argument is valid in virtue of its K-form alone. Privileging the psychological (italicized) vocabulary in ‘Smith has a mind, minds process information, therefore Smith processes information’, and varying its non- psychological terms, we can produce inferences that are good in virtue of their psychological form such as ‘Juarez has a mind, minds process information, therefore Juarez processes information’. On this account, a formally valid inference is just a special kind of materially valid inference—in particular, the kind where the material validity holds in virtue of the conceptual contents of the logical vocabulary. Such inferences cannot be rendered materially invalid by varying their nonlogical terms. Logical validity is a species of material validity.

§3.2 Semantic Inferentialism

Brandom’s inferentialist theory understands meaning in terms of role in reasoning, specifically with respect to material inferential relations. An important implication of this view is that a thinker needs to have many concepts in order to have any one in particular:

For grasping a concept involves mastering the proprieties of inferential moves that connect it to many other concepts: those whose applicability follows from the applicability of the concept in question, those from whose applicability the applicability of the target concept follows, those whose applicability precludes or is precluded by it. One cannot have just one concept. This holism about concepts contrasts with the atomism that would result if one identified concepts with differential responsive dispositions. (1994: 89)

Brandom’s inferentialism is designed to answer an important question about what is distinctive about sapience—i.e., about what it is to grasp something conceptually (1994: 4-5). To identify

36 the understanding of a concept with reliable differential responsive dispositions, e.g., the disposition to utter ‘dog’ upon the presentation of a dog, will not do. One does not have the concept DOG unless one understands, e.g., what is entailed by the proposition ‘X is a dog’ (e.g., that ‘X is an animal’), and what it precludes (e.g., that ‘X is an air conditioner’). In short, one needs to understand the inferential role of a concept in order to grasp that concept, and one does not understand the inferential role of a concept unless one grasps many of the other concepts which figure in that inferential role.

Brandom’s account of material inference differs from Sellars’ in the following two respects. While Sellars spoke of material rules of inference, and considered them to be “as essential to meaning” as are formal rules of inference (1953/2007: 7, 25), Brandom argues that material inferential relations alone determine meaning and that our understanding of those relations does not originate in an explicit awareness of linguistic rules—that kind of understanding only comes to the fore in the context of logical discourse, as we saw in §3.1. The terminological difference here is just that.8 I mention it in order to emphasize that it’s a crucial feature of Brandom’s theory of language that our grasp of material inferential relations is, to begin with, implicit in practice.

Brandom’s inferentialist semantics is a use-theory of meaning: he explains the semantic features of conceptual content in terms of normative-pragmatic features that are implicit in concept-use. The idea here is to account for conceptual relations such as ‘P implies Q’, and ‘P implies not-R’ in terms of practices that involve treating ‘Q’ and ‘not-R’ as consequences of

8 Sellars (1954), following Wittgenstein (1953), recognized that any account of meaning given in terms of rule- following must appeal to some aspects of linguistic behavior which are more basic, on pain of infinite regress (if one has to follow a rule in order to learn to follow a rule, then one would have to learn the meta-rule for that rule, which would in turn require learning the meta-meta-rule for that meta-rule, and so on).

37 ‘P’ (1994: 182-84). Suppose Juarez tells Smith that she believes that climate change is the result of greenhouse gas emissions and land-clearing. Juarez’s utterance has pragmatic significance— if Smith is educated on the issue, then he will take Juarez to be committing herself to the view that human beings are responsible for climate change, that climate change is not just a “natural cycle,” that greenhouse gas emissions and land-clearing can have the same effect on the atmospheric greenhouse, and so on. If Smith is like-minded, he will take Juarez to be entitled to, i.e., justified in asserting, the abovementioned claims.

It is in virtue of the normative practices that concept-users engage in, of taking linguistic performances to have pragmatic significance by attributing commitments and entitlements to one another, that those performances are inferentially articulated and hence conceptually contentful

(1994: 187-190). The inferential relations, which, on this view, constitute meaning arise out of our normative practices. Formal relations come into the picture later, when we use logical concepts to make those inferential relations explicit, which in turn renders them open to rational criticism.

Expressing them in this sense is bringing them into the game of giving and asking for reasons as playing the special sort of role in virtue of which something has a conceptual content at all— namely an inferential role, as premise and conclusion of inferences. (1994: 106)

The speech act of assertion, on Brandom’s view, is the basic unit of discursive, linguistic performance:

The position maintained here is that discursive (in the Kantian sense of concept-mongering) practice can only be linguistic practice, and that what distinguishes a practice as specifically linguistic is that within it some performances are accorded the significance of assertions. It is only because some performances function as assertions that others deserve to be distinguished as speech acts. The class of questions, for instance, is recognizable in virtue of its relation to possible answers, and offering an answer is making an assertion––not in every individual case, but the exceptions (for example, questions answered by orders or by other questions) are themselves intelligible only in terms of assertions. Orders or commands are not just performances that alter the boundaries of what is permissible or obligatory. They are

38 performances that do so specifically by saying or describing what is and is not appropriate, and this sort of making explicit is parasitic on claiming. (1994: 172, emphasis in original)

The intelligibility of all of the various language games (questioning, commanding, requesting, thanking, etc.) that speakers engage in depends essentially on the intelligibility of asserting—we can only make and understand commands, requests, promises, and so on if we can make and understand assertions. But the converse, on this view, is not the case: the intelligibility of asserting is independent of that of all other speech acts. The act of asserting is what Brandom calls an “autonomous discursive practice,” viz., “a language game one could play though one played no other (2008: 27).

Corresponding to this pragmatic thesis about linguistic use is a semantic thesis about conceptual content, namely, that assertions/propositions are the basic units of meaning; the conceptual contents—inferential roles—of expressions, mental states/attitudes, and performances are comprised of propositions (1994: 79-84). Propositions are inferentially related to other propositions—they are the nodes in the network of material inferential relations, which, on

Brandom’s view, constitute the conceptual contents of a language.

It will be helpful to mention a bit about Kant’s influence on Brandom in order to clarify these last few points. Kant understood the distinction between sentience (sensuous awareness) and sapience (conceptual awareness) in deontic terms. The difference between rational, socio- linguistic, concept-using beings and merely sentient ones is that the former are capable of making judgments and performing actions—only they incur responsibility for their judgments and actions:

What is distinctive about judgings and doings—acts that have contents that one can take or make true and for which the demand for reasons is in order—is the way they are governed by rules. They are conceptually contentful and so are subject to evaluation according to the rules that express those contents. Being in an intentional state or performing an intentional action

39 accordingly has a normative significance. It counts as undertaking (acquiring) an obligation or commitment; the content of the commitment is determined by the rules that are the concepts in terms of which the act or state is articulated. Thus Kant’s version of the…demarcation criterion…picks us out as distinctively normative, or rule-governed creatures. (1994: 8-9)

The pragmatic and semantic primacy that Brandom, following Kant, accords to acts of assertion, then, issues from the fact that one cannot be held responsible for linguistic utterances that are smaller than judgments—if, out of the blue, one utters “uh,” “street,” or “apple,” one has not thereby taken on any commitments. Assertions are the basic, minimal units of meaning because they are the “minimal units of responsibility—the smallest semantic items that can express commitments” (2008: 34). Asserting is what one has to do in order to say anything at all.

Recall from §3.1 that the role of logical vocabulary, on Brandom’s expressivist account, is to make explicit the material proprieties of inference that are already implicit in linguistic use

—to clarify the inferential commitments speakers become entitled to in the course of ordinary assertional practices. It follows on this account that assertions can be made and understood, and therefore meaningful communication can occur, independently of the use of any logical vocabulary:

It would be a mistake to conclude from the true premise that something can be thought of as propositionally contentful only in virtue of its relation to proprieties of inferential practice, to the conclusion that such practice must be logically articulated. Such a move depends on the formalist error of assimilating all correctnesses of inference to logical correctness of inference, thereby denying the possibility of material, content-conferring inferential proprieties. Material proprieties of inference are antecedent to formal proprieties of inference in the order of explanation, because to say that an inference is valid or good in virtue of its K form (for instance logical form) is just to say that it is a (materially) good inference, and it cannot be turned into one that is not good by replacing non-K (for instance nonlogical) vocabulary by (syntactically cocategorial) non-K vocabulary. There is nothing incoherent about a language or stage in the development of a language in which the only vocabulary in play is nonlogical. (1994: 383, emphasis in original)

Logical discourse, on this view, is non-autonomous: it is not a language game one could play though one played no other.

40 Sellars’ argument (§2) shows that formal validity cannot be the sole standard for rational inference. Brandom’s expressivism further decenters formal proprieties of inference, both with respect to their role in reasoning and to their importance for meaning. Rational inference is, in general, materially good inference—formal validity is a species of material validity.

Furthermore, the conceptual contents involved in language and thought are inferentially articulated, and hence meaningful—and hence rational—in virtue of their correct use in ordinary assertional practices. By contrast to the formalist conception of rationality, according to which all rational inferences are formally valid inferences, Brandom holds that is because we take inferences to stand in certain material inferential relations and not others that we endorse some inferences and not others. These include relations of:

Material Consequence: where a commitment to P obliges a commitment to Q, Material Compatibility: where a commitment to P permits but does not oblige a commitment to Q, and Material Incompatibility: where a commitment to P obliges a commitment to not-Q.

Rationality consists in mastery of those [assertional] practices. It is not to be understood as a logical capacity. Rather, specifically logical capacities presuppose and are built upon underlying rational capacities. The fundamental characteristic role of logical vocabulary is to make it possible to talk and think explicitly about the inferentially articulated semantic contents implicitly conferred on expressions (among other things) by their role in rational practice. The optional introduction of sophisticated logical explicitating vocabulary has an expressive point and payoff. By its means the material inferential practices which govern and make possible the game of giving and asking for reasons, are brought into that game (and so into consciousness) as explicit topics of discussion and justification. (1994: 117)

To be sure, Brandom’s rejection of formalism is not a rejection of the importance of logic

(neither, for that matter, is the more wide-ranging rejection of formalism presented in this essay).

Rather, it’s a rejection both of the idea that reasoning is essentially formal in nature, along with the corresponding view that logical validity is the sole measure of rationality—in short, logic is

41 not the engine of human reason. Nonetheless, it is, on Brandom’s view, a centrally important socio-linguistic tool:

Having to do without logical expressions would impoverish linguistic practice in fundamental ways…The task of forming and nurturing the concepts we talk and think with is brought out of the dim twilight of what remains implicit in unquestioned practice into the daylight of what becomes explicit as controversial principle. Material contents, once made explicit, can be shaped collectively, as interlocutors in different situations, physically and doxastically, but in concert with their fellows, provide objections and evidence, claims and counterclaims, and explore possible consequences and ways of becoming entitled to assert them. Logic is the linguistic organ of semantic self-consciousness and self-control. The expressive resources provided by logical vocabulary make it possible to criticize, control, and improve our concepts. To give this up is to give up a lot. (1994: 384)

We’ll see in the next chapter (§4.1) that Mercier and Sperber hold a similar view of the relationship of logic to reasoning.

§4 Conclusion

The views by Sellars and Brandom introduced here—logical expressivism and semantic inferentialism—provide an alternative to formalist ways of thinking about the nature of reasoning, and about the relationship between logic and reasoning. Formalists in psychology and cognitive science are committed to explaining the nature of reasoning in terms of innate logical machinery. In philosophy, formalists seek to explain the nature of rationality in terms of grasp of logical principles. On the alternative Sellarsian/Brandomian picture presented in this chapter, reasoning is taken to be essentially content-based, rather than formal in nature, and logic’s relationship to reasoning is understood as an expressive one.

Inferentialism is a systematic theory that integrates views on the nature of reasoning, linguistic use and meaning, and logic—a suitable conceptual framework for a non-formalist theory of reasoning. What’s lacking in inferentialism is an empirical account of the content-

42 based, social nature of reasoning. As it turns out, Mercier and Sperber (2017) have just such an account. In this next and final chapter, I’ll draw connections between their interactionist theory of reasoning and Brandom’s inferentialism. In addition, I’ll point out the ways in which these two views can supplement one another, each providing what the other lacks.

By integrating inferentialism, which provides a systematic conceptual framework for thinking about the nature of rational inference, with interactionism, an empirical theory of the nature of reasoning, we will have arrived at a substantive alternative to formalism. We’ll also have a new perspective from which to view debates in cognitive science. I’ll conclude with a discussion of LOTH, and of the relationship between reasoning and the vexed issue of modularity.

43 3 Inferentialism and Interactionism

§1 Introduction

In the last chapter, we looked critically at formalism from a Sellarsian/Brandomian philosophical perspective. I’ll build on that critique here, this time from a psychological perspective. My aim is to show that, in addition to falling short when it comes to accounting for subjunctive conditionals and explaining the nature of formal validity, the formalist approach— which Mercier and Sperber refer to as “intellectualism”—is premised on a fundamental error with regard to its view of the adaptive socio-evolutionary function of human reasoning. Mercier and Sperber (M&S) argue that the capacity to reason did not—indeed, could not have—evolved as a mechanism geared towards the formal derivation of truths. They suggest, rather, that reasoning evolved for specifically social purposes, chief among which is social argumentation.

§2 The Interactionist Theory of Reasoning

In The Enigma of Reason (2017) (henceforth ER), M&S put forward an avowedly non- formalist theory of reasoning. They point out that formalist research programs in psychology have led to widespread confusion about the nature of human reasoning:

Reason as standardly understood is doubly enigmatic. It is not an ordinary mental mechanism but a cognitive superpower that evolution—it used to be the gods—has bestowed only on us humans. As if this were not enigmatic enough, the superpower turns out to be flawed. It keeps leading people astray. Reason, a flawed superpower? Really? (2017: 4)

44 It’s puzzling, from an evolutionary point of view, that we would evolve a unique cognitive capacity that is systematically flawed. Why would reasoning, unlike other cognitive processes such as perception, attention, and memory, be so consistently unreliable? M&S argue that the problem here is not that we are bad at reasoning, but that the formalist paradigm is an unrealistic theory of both how reasoning works and what it is for.

On their alternative theory, interactionism, reasoning has two main functions. One is to produce publicly consumable reasons which serve to justify one’s claims and actions to others, in an attempt to facilitate social coordination,

By giving reasons to explain and justify yourself, you do several things. You influence the way people read your mind, judge your behavior, and speak of you. You commit yourself by implicitly acknowledging the normative force of the reasons you invoke: you encourage others to expect your future behavior to be guided by similar reasons (and to hold you accountable if it is not). You also indicate that you are likely to evaluate the behavior of others by reasons similar to those you invoke to justify yourself. Finally, you engage in a conversation where others may accept your justifications, question them, and invoke reasons of their own, a conversation that should help you coordinate with them and from which shared norms actually may progressively emerge. (2017: 185-186)

The other is to evaluate reasons offered as justifications for the claims and actions of others, in order to ensure successful communication,

The argumentative use of reasons helps genuine information cross the bottleneck that epistemic vigilance creates in the social flow of information. It is beneficial to addressees by allowing them to better evaluate possibly valuable information that they would not accept on trust. It is beneficial to communicators by allowing them to convince a cautious audience. (2017: 194)

Humans are social creatures, and in order to thrive in a social setting, we had to rely on others— not only on those who we were already inclined to trust (via kinship, for instance), but also on those we had no prior inclination to trust, such as strangers who may have had it in their interest to deceive us. The function of reasoning in these situations is to assess the relationships between reasons and conclusions, both theoretical and practical. We can convince others to trust us by providing reasons that––we predict they will take to––support our claims and actions. And we

45 can evaluate the reasons offered by others by “intuiting” the degree of support we take those reasons to give to the claims and actions that they are seeking to justify. Lastly, we intuit further reasons that support or call into question those claims or actions, and the reasons being provided for them. This is what reasoning is for on the interactionist theory. We’ll now see how, according to M&S, reasoning works.

All cognitive processes involve one or another sort of inference, which M&S define as

“the extraction of new information from information already available, whatever the process” (2017: 53). Beyond the acquisition of sensory information, cognitive creatures use highly specialized inferential mechanisms to exploit that information. Each of these mechanisms

—what M&S will call “modules”—are designed, either through evolutionary processes or in the course of learning, to detect certain relevant inputs—regularities in the target environment—in order to produce relevant outputs (useful information), and to make those outputs available for use by other modules (87). This is how creatures with cognitive systems cope with their environments.

A hungry dog, for example, will take the presence of its owner as a highly relevant input.

It has a module—i.e., a reliable mechanism—that tracks regularities between the presence of its owner and the presence of, say, food. The dog sees its owner, and forms an expectation—i.e., draws the inference—that food is on the way. At the same time, many other modularized inferential processes are engaged, e.g., the module for vision, in order for the dog to see its owner, and the module for locomotion, which allows the dog to approach or avoid. In short, all cognitive processes involve inferential procedures that apply to either representations or, at least, to detected regularities in an environment. Animals need not represent a regularity in order to

46 exploit it. Some inputs, such as the presence of snakes, for instance, induce an automatic fear response in animals that have an innate or a conditioned fear of snakes (2017: 87).

Reason and intuition are often contrasted as though they are distinct cognitive mechanisms, as is the case in dual process theory. M&S reject this dichotomy flat out. On their view, reason and intuition are both forms of inference. Moreover, to reason is to draw intuitive inferences about a specific domain of represented objects—i.e., reasons themselves—by means of a module whose function it is to draw such inferences (2017: 96). It's worth going over this point slowly.

We can represent all sorts of objects: trees, colors, states of affairs, unicorns, etc. But we can also (meta)represent our representations of those objects: the idea of a tree, color words, and propositions (92). The domain of the reasoning module consists of a particular kind of metarepresentation—i.e., reasons. Reasoning, then, is the primary function of a metarepresentational module designed to draw intuitive inferences about a special class of things, viz., those things we call reasons.

What’s distinctive about intuitions, on the interactionist account, are their accompanying metacognitive feelings (2017: 66). The outputs of inferential processes sometimes manifest themselves to us as intuitions, and when this happens, we will feel more or less confident in upholding them. But we will have no awareness of the inferential processes that produced those conclusions. This is because those processes are performed by sub-personal mechanisms, which operate below the level of conscious awareness (see Pereplyotchik, 2017: 163-167).

The intuitive inferential processes that, on the interactionist account, enable us to engage in reasoning, then, are opaque—we have no introspective access to them. Furthermore, the kind

47 of role that we often accord to reasons in explanations of our beliefs and decisions to act is, in an important sense, fictitious. Although we often think of ourselves as believing and deliberately acting on the basis of already-explicit reasons, structured in a language-like format, it is actually far from obvious that this is the case.

Why do you think this? Why did you do that? We answer such questions by giving reasons, as if it went without saying that reasons guide our thoughts and actions and hence explain them. These reasons are open to evaluation: they may be good or bad. Good reasons justify the thoughts or actions that they explain. This picture of the role of reasons in explanation and in justification may seem self-evident. It is based, however, on a convenient fiction: most reasons are after-the-fact rationalizations. (2017: 109)

Our actions and claims are preceded by many inferential processes, but the production of reasons

(as characterized above) is an inferential process in its own right. It is aimed at justifying our actions and claims to others. But it usually occurs after an action or claim has already been performed or made—i.e., when a commitment has become explicit in speech or action. Of course, some reasoning (again, in the technical sense of the term that M&S recommend) may take place before an action is performed, but typically not before the initial decision to act has been formed.

We might hesitate, for example, to act on a decision that will have reputational consequences (2017: 123-124). In such cases, reasoning does play a role in what leads up to the performance or nonperformance of an action, viz., we intuit potential consequences for our reputations. But it would be inaccurate to say that it’s because––in a causal sense—of those reasons that we act. Rather, we infer that our reputations are at stake in some way, and we act to preserve our social standing. As M&S put the point, “living up to the story you want to be able to tell about yourself isn’t quite the same thing as telling a true story” (2017: 124).

48 On this account, we do not arrive at our beliefs and decisions to act by reasoning. Those mental states are the results of intuitive inferential processes aimed at exploiting regularities in the environment. But they are not outputs of the reason module, whose job, in the context of offering explanations and/or justifications, is to intuit reasons that support conclusions and, in the context of evaluating explanations and justifications, to judge the degree to which what are taken to be reasons support the conclusions that others have drawn. This, I take it, is what is meant by

Brandom's phrase “the game of giving and asking for reasons.”

We’ve seen that reasoning, on the interactionist theory, is, by its very nature, a fundamentally social activity. Its primary functions are to justify and to evaluate—activities that are both social in nature. The beliefs and decisions that figure in this practice can be evaluated by reasoning, but reasoning does not lead solitary reasoners to those beliefs and decisions in the first place. Moreover, contra formalism, the conclusions of reasoning are not generated by domain-general logical procedures, but by modular processes of intuitive inference.

In the next section, I’ll argue that interactionism and inferentialism complement one another, despite employing quite distinct methods of inquiry—one a priori and broadly

“conceptual,” the other overtly empirical. In tandem, I believe that they provide us with a satisfying picture of reasoning and rationality, or at least an outline of a framework that can—and

I think should—be profitably pursued by philosophers of language and mind.

49 §3.1 Connections

We now come to what I take to be two of the most important connections between inferentialism and interactionism: (i) a commitment to the explanatory priority of material over formal inferences, and (ii) a commitment to the theoretical significance of the social dimension of reasoning. Despite being disparate research programs, both of these theories are in agreement with regard to these two fundamental issues. I think, moreover, that each theory has something to offer the other. Interactionism provides the empirical details lacking in inferentialism, and inferentialism provides a far richer account of the social norms that underwrite the justificatory and argumentative performances at the center of the discussion in ER.9

With regard to (i), I claim that the modular view of reasoning which M&S present in ER is the empirical analog to the inferentialist view that reasoning is a material inferential process.

The contents of claims and judgments, on the inferentialist view, are constituted by the material inferential relations that hold between them. On the interactionist view, the contents of reasoning consist of intuitions about reasons, i.e., of intuitions about whether reasons confirm or disconfirm conclusions.

I want to suggest that intuitions about reasons are intuitions about the material inferential relations that hold between premises and conclusions. When we consider the inference ‘It’s raining, therefore the streets will be wet’, the reason module draws on information about rain stored in the mind—in our “mental file” for rain (ER: 97-99)—and intuits a rational connection between the premise and the conclusion of that inference, because one piece of information that we have stored about rain is that it causes wet streets. We endorse inferences when they fit with

9 Notably, Brandom’s Making it Explicit (a book nearly 800 pages in length) does not contain a single empirical reference.

50 the information that we have stored about their contents in our mental files—i.e., when we find them to be materially valid.

Despite terminological differences, inferentialism and interactionism agree on the nature of human reasoning: it’s content-based, rather than formal in nature. Furthermore, the account of reasoning in ER provides empirically plausible grounds for purely theoretical Sellarsian/

Brandomian claims about reasoning. We now have a story not just about what it is that we are able to do, but also a story about how we do it. We reason in order to keep track of our commitments and entitlements, as well as those of others, and we do it by means of a module shaped by evolution for that very purpose.

As for (ii), both interactionism and inferentialism tell essentially the same story about the role that judgments/intuitions about rational relations play in norm-governed, socio-linguistic practices. Recall that Brandom shares with Kant the view that propositions are the fundamental units of meaning, because reasoning is an essential linguistic practice, and only propositions can play the role of premises and conclusions in arguments. On these grounds, Brandom argues, contra Wittgenstein, that language does, in fact, have a “downtown”—i.e., the distinctively social practice of giving and asking for reasons (2008: 43; 2013: 175). By making an assertion, a person takes on a distinctive kind of complex socio-normative status—namely, a commitment to justifying that statement, by exhibiting further claims that entitle him or her to it, as well as a commitment to accepting the materially good inferential consequences of that statement.

Let’s consider an example: If I claim that X is a dog then I commit myself to justifying this claim, e.g., by reference to X’s appearance; I also commit myself to accepting ‘X is an animal’,

‘X is not a heavy metal song’ and indefinitely many other possible judgments (should the

51 question arise). I also entitle others to take me to task for making any further materially incompatible commitments. If I say “X is a dog,” I preclude myself from being entitled to say “X is a black hole.” M&S make essentially the same point in the following passage:

When we give reasons for our actions, we not only justify ourselves, we also commit ourselves. In the first place, by invoking reasons, we take personal responsibility for our opinions and actions as described by us, that is, as attitudes and behavior that we had reasons to adopt. We thereby indicate that we expect others to either accept that we are entitled to think what we think and do what we do or be ready to challenge our reasons. (2017: 126, emphasis added)

Since both inferentialism and interactionism see reasoning as a fundamentally social activity, both require an account of the social norms that underwrite the performance of giving reasons.

And while inferentialism can benefit from the kind of empirical support that interactionism seems to enjoy, the latter can benefit in turn from Brandom’s detailed account of the relevant social norms, which goes far beyond the minimal statements that M&S make about this topic.

§3.2 Normative Pragmatics

In Making it Explicit (1994), Brandom provides a systematic exposition of the normative structure that comes into view when one takes on the explanatory task of grounding an inferentialist semantics in a normative pragmatics. Brandom accounts for linguistic meanings in terms of their roles in reasoning, and reasoning, in turn, is accounted for in terms of the socio- normative statuses of commitment and entitlement. The inferential relations holding between commitments and entitlements place normative constraints on discursive activity—both thought and language.

52 Thinking or speaking rationally, on Brandom’s view, is a matter of making the correct moves in what I earlier called “the game of giving and asking for reasons.” The first and more generic version of this idea was advanced by David Lewis (1979), who devised a “scorekeeping” model of linguistic practices. Brandom (a student of Lewis’s) went on to develop a distinctively inferentialist version of the scorekeeping model,

In scorekeeping terms, the significance of a speech act consists in the way it interacts with the deontic score: how the current score affects the propriety of performing the speech act in question, and how performing that speech act in turn affects the score. Deontic scores consist in constellations of commitments and entitlements on the part of various interlocutors…Being rational—understanding, knowing how in the sense of being able to play the game of giving and asking for reasons—is mastering in practice the evolution of the score. (1994: 183)

This notion of “deontic scorekeeping” is central: it involves agents keeping track of the material inferential relations between their own commitments and entitlements and those of others. With this notion in hand, Brandom provides a systematic picture of the justificatory and argumentative social practices that M&S only hint at in their discussion (ER: 127). Incorporating these ideas into the interactionist framework provides interactionism with a more robust picture of the normative elements that are involved in viewing reasoning as a fundamentally social activity.

Knowing how we do what we do is only valuable insofar as it sheds light on what it is that we do. What’s missing from the interactionist picture of reasoning that we find in ER is an account of the relationship between social performances—what we are able to do, i.e., commit ourselves to entitlements—and conceptual content: what it is that we commit ourselves to.

Without a detailed pragmatic theory of commitment and entitlement, the interactionist picture lacks the normative component that it needs in order to tell a unified story about human sapience

—one which accounts for the integral relationships between reasoning, conceptual content, and the social practices in which these relationships figure prominently.

53 On the formalist views of reasoning discussed in chs. 1-2, rational reasoning (as opposed to mere association) is geared toward the acquisition of true beliefs primarily through the use of formal principles. The social aspects of reason are accorded little or no theoretical significance

(as in both Descartes’ Meditations on First Philosophy and his Rules for the Direction of the

Mind), because reasoning is understood as the solitary mind’s attempt to arrive at truths about the world. M&S rehearse the many compelling arguments against this picture of reasoning that have been launched since Descartes and develop many novel ones, original to the interactionist approach.

It is implausible that we would have evolved a cognitive capacity whose main function is to discover truths about the world, and yet be consistently unreliable when it comes to solving basic logical and statistical problems. On the other hand, it makes good sense, from an evolutionary perspective, that we would have evolved a cognitive capacity that enables us to justify our own claims to others and to evaluate their claims for reliability, accuracy, and trustworthiness. As noted earlier, trust between individuals is a prerequisite for social coordination, and trust is secured—provisionally, at least—through persuasion, i.e., reasoning

(see Thagard, 2000 and Kuhn, T. S., 1962). But individuals must also maintain a sufficient degree of epistemic vigilance, lest they be deceived. So, in addition to persuasion, a mechanism for reasoning with others should also be geared towards skeptical evaluation.

To be sure, the interactionist account of reasoning is, in many ways, contentious, given the dominance of formalism in both philosophy and psychology. But I have argued that there are strong reasons for pursuing this alternative, in light of the convergence between careful

“armchair” theorizing and evolutionary psychology. Let me now turn to what I see as some of

54 the most significant implications of this hybrid inferentialist-interactionist view. In particular,

I’ll examine its impact on two longstanding debates in cognitive science. The first concerns whether there’s a Language of Thought in the sense of Fodor (1975). The second is about whether a modular account of reasoning is plausible, given its “global” character (Fodor, 1983;

2001).

§4.1 Reasoning and Mentalese

Recall from ch. 2 that Sellars (1953/2007) put forward arguments that cast strong doubts on the plausibility of formalism. But philosophers have nevertheless proceeded as though the formal paradigm is the correct model of human reasoning. Fodor (1975, 1987) advanced what is now the most popular version of the formalist approach in philosophy, namely, The Language of

Thought Hypothesis. According to LOTH, thoughts are represented by physical symbols in the brain. These symbols are syntactically structured and semantically “locked on” to the external world. To think, according to this picture, is for the brain to manipulate these symbols through the application of formal rules, defined solely over the logical form or structure of the so-called

“Mentalese” sentences. Formal rules, in the sense intended here, are not sensitive to the semantic content of representations. But since Mentalese sentences are supposed to be syntactically structured (on analogy with public-language sentences), the application of purely formal rules results in logically valid inferences that preserve the semantic contents of the

Mentalese representations—paradigmatically, truth.

55 Sellars’ argument, discussed earlier, should give us pause as to the plausibility of LOTH.

We saw in ch. 2 (§2) that the formalist approach has trouble with subjunctive conditionals, which cannot be rendered in a non-modal fashion without losing their distinctive meanings. Something very similar is true of Fodor’s “metasemantics” for Mentalese concepts—what he calls the

“asymmetric dependence” theory (Fodor, 1990). Besides suffering from a variety of well-known internal difficulties, it is fundamentally incomplete, as it offers no account of the meanings of logical and modal terms. Indeed, it is perhaps precluded from doing so in principle, despite making liberal use of it in the formulation of the theory itself (cp. Brandom, 1994: ch. 8). Given the plain fact that subjunctive conditionals permeate ordinary and scientific speech, a theory of meaning that has no clear resources for accommodating them is inadequate. And if the theory itself makes use of logical and modal vocabulary, then it is incomplete.

In ch. 3, I showed how Sellars’ view paves the way for a distinctively expressivist account of logical vocabulary, in the following important sense. The vocabulary of formal logic

—paradigmatically, the connectives, quantifiers, and modal operators—allows us to express explicitly the previously implicit proprieties of material inference that hold between judgments— i.e., to make explicit the commitments and entitlements that are implicit in our assertions and inferences. And this is what, in turn, allows for such proprieties to be examined publicly, via the socio-pragmatic mechanisms of offering, consuming, and evaluating ever-higher-order reasons for and against their continued use.

If this is the case, then the door is open to seeing formal deductions as schematized material inferences, whose material propriety is underwritten by the contents of distinctively logical concepts. In light of this theoretical alternative, formalism looks like a backwards

56 approach to explaining human reasoning. Logic is not the engine of human reasoning, but rather an important and distinctive socio-linguistic tool—one that allows us to express our arguments in a form that renders their implicit material inferential relations explicit, and thereby open to rational criticism on the part of a public audience. M&S express a similar view in the following passage: “The main role of logic in reasoning, we suggest, may well be a rhetorical one: logic helps simplify and schematize intuitive arguments, highlighting and often exaggerating their force” (2017: 7). I have pointed out as well that M&S share with Sellars and Brandom a commitment to the primacy of material over formal inference,

It is commonly assumed...that most, if not all, ordinary reasoning arguments must, to be arguments at all, correspond to syllogisms; if the correspondence is not manifest, then it must be implicit; some premises must have been left out for the sake of brevity. Most ordinary arguments are, according to this view, “enthymemes,” that is, truncated syllogisms. This, we will argue, is just old dogma, so much taken for granted that little or no effort is made to justify it empirically. (2017: 37)

The combination of these arguments from inferentialism and interactionism together constitutes a strong challenge to the formalist approach.

§4.2 Reasoning and Massive Modularity

One important implication of interactionism, in particular, concerns a debate in cognitive science over the relationship between reasoning and modularity. Fodor (1983) articulated one of the earliest modular accounts of the mind in cognitive science. On that picture, modules are domain specific, that is, sensitive only to particular kinds of information, and informationally encapsulated, i.e., they can access only certain types of information (1983: 69). A module whose function is, say, to recognize the faces of conspecifics, takes as visual input only those faces, and

57 processes that input in isolation of information contained elsewhere in the system (1983: 47).

Non-modular processes, by contrast, are sensitive to a variety of inputs—e.g., the executive component of working memory draws on information about perceptual content across all of the sense modalities (Carruthers, 2015).

More generally, central processing, or non-demonstrative reasoning, is distinguished from modular processing by virtue of two properties. It is Quinean, i.e., sensitive to the global properties of a belief system (such as simplicity and coherence), and it is isotropic: in principle, a change in any one belief can be relevant to any other belief contained in the system (1983: 105,

107). Reasoning, on Fodor’s view, is a domain-general process—it requires global consideration of information across modules. A module for reasoning, then, would need to have access to all of the information stored in the mind in order to engage in reasoning (Fodor, 2000).

M&S also adopt a version of the modularity hypothesis, but not the one Fodor (1983) develops. Theirs is an instance of what has come to be called the “massive modularity” approach, which posits modules where Fodor argued for processes with a domain-general structure—the so-called “central system.” Since modules have access to only specific kinds of information, the prospects for a modular account of reasoning would seem dim. But M&S have a response to Fodor’s argument. It rests on an important but difficult distinction between the

“actual domain” of a module—reasons—and its “virtual domain,” which can include anything those representations are about (2017: 101).

If you intuitively grasp that 900 is three times 300, your intuition is driven by properties of the numerals, but the relevant information you gain is about the numbers these numerals represent. If you recognize the cogency of a good explanation of, say, how a dual-technology motion detector works, then you have learned something not just about the explanation but also, and more importantly, about motion detectors. (103)

58 To use another simple example, suppose that I move to a new climate and encounter snow for the first time, and I’m told that if I drive too fast on icy roads, then my car will slide.

The reason module will metarepresent the fact that driving fast on icy roads leads to sliding as a reason not to drive too fast. The actual domain of reasoning consists only of pieces of information that are metarepresented as reasons that confirm (or disconfirm) conclusions. But the virtual domain of reasoning consists of any piece of information—knowledge of facts, laws, principles, properties, meanings, etc.—that might be taken as a reason for or against a conclusion. It is in virtue of this relationship between the actual and virtual domains that we can gain knowledge through reasoning. So, for example, if I learn that ice being on the roads is a reason not to drive too fast, I also gain knowledge with respect to the contents metarepresented, namely, knowledge of causal relations holding between ice, cars, and driving speed.

With this distinction between actual and virtual domains in hand, M&S can reply to

Fodor that the reason module need not have a computationally intractable actual domain—it takes as inputs representations produced by other modules, which stand in (dis)conformational relations to conclusions, and metarepresents them as reasons for or against those conclusions.

Their solution does require dropping encapsulation, as Fodor understood the notion, as a constraint on modular processing, since the reason module must be able to take as inputs the representational outputs of other modules. But Fodor-style modularity isn’t the only kind out there.

Carruthers (2006), for instance, argues that computational frugality allows for “wide- scope” encapsulation. In Fodor’s—“narrow”— sense, a modular process is encapsulated in that most of the information contained in the mind cannot affect its processing. Understood in a

59 “wide” sense, however, a module need only be encapsulated in such a way that it’s processing is not affected by most of the information contained in the mind. In this latter sense, the restriction is applied to a module’s processing, rather than the information that it processes. So long as a modular process is somehow restricted in the range of information that it can take as input, that processing will be computationally tractable. To bring the point back to M&S, the reason module is so restricted in its range of inputs. It’s domain-specific, in that it takes representations as inputs, as well as encapsulated (in the wide-sense) because it doesn’t take all representations into account during a single instance of reasoning—just those that confirm or disconfirm the conclusion in question.

Conclusion

My goal in the pages above has been to develop and promote an approach to reasoning and rationality that stands as a plausible alternative to the dominant formalist perspective. The approach integrates Brandom’s inferentialist theory of language with M&S’s interactionist theory of reasoning. Along the way, I highlighted some of the pitfalls of formalism and the ways in which the inferentialist and the interactionist approaches avoid them.

The first shortcoming of formalism that we saw is its inability to account for subjunctive conditionals, as Sellars pointed out (ch. 2, §2). Since subjunctive conditionals are the expressions of material rules of inference, Sellars proposed that we reject the formalist approach as an inadequate model of human reasoning, and recognize material rules of inference as a source of rational authority in their own right, independent of that of formal rules of inference.

60 Brandom developed Sellars’ line of thought further and showed how one can give an account of formal validity in terms of material validity (ch. 2, §3.1). To say that an inference is formally valid is just to say that one can hold the logical terms of an argument fixed while varying the nonlogical terms, and never produce a materially invalid inference. Formalists, on the other hand, have no alternative explanation on offer of the nature of logical validity, and perhaps cannot have one, since that’s the only kind of validity that they recognize (giving an account of something in its own terms is not an explanation). So, formalist explanations of the nature of rational inference in philosophy fall short—they cannot account for inferences that make use of subjunctive conditionals, and they have no explanation of the nature of formal validity (which is a substantial shortcoming for a theory which identifies rational inference with logical inference).

In psychology, the formalist faces the problem of explaining how we could evolve the capacity to reason, understood as a formal-computational process in nature, and yet be so inept at formal reasoning—this is “the enigma of reason.” But as we saw in ch. 3 (§2), M&S argue that the real problem is that psychologists of reasoning have misidentified the function of reasoning.

On their view, reasoning is a modular process of intuitive inference geared towards the justification and evaluation of claims and actions in social contexts, rather than a “flawed superpower” aimed at deriving truths. M&S make a strong case for this claim, and if they are right, then the various formalist theories discussed in ch. 1 (MLH, DPT, and LOTH) are premised on a mistaken view of the nature of human reasoning, viz., that it is formal and solitary in nature, rather than an essentially content-based, social activity.

61 On both of the alternative, non-formalist accounts of reasoning—inferentialism and interactionism—presented in chs. 2-3, solitary reasoning is derivative from social reasoning, as the following passages by Brandom and M&S make clear:

Logicians typically think of inference as involving only relations among different propositional contents; not as also potentially involving relations among different interlocutors. However, discursive practice, the giving and asking for reasons, from which inferential relations are abstracted, involves both intercontent and interpersonal dimensions…The conceptual contents employed in monological reasoning, in which all the premises and conclusions are potential commitments of one individual, are parasitic on and intelligible only in terms of the conceptual contents conferred by dialogical reasoning, in which the issue of what follows from what essentially involves assessments from the different social perspectives of interlocutors with different background commitments. Representationally contentful claims arise in the social context of communication and only then are available to be employed in solitary cogitation. (Brandom, 1994: 496-497, emphasis in original)

In our interactionist approach, the normal conditions for the use of reasoning are social, and more specifically dialogic. Outside of this environment, there is no guarantee that reasoning acts for the benefits of the reasoner. It might lead to epistemic distortions and poor decisions. This does not mean reasoning is broken, simply that it has been taken out of its normal conditions. (Mercier and Sperber, 2017: 247)

Additionally, both theories take reasoning to be content-based, rather than formal in nature.

The formalist line of thought begins with explicit propositional licenses that license inferences in virtue of their logical form. Material inferences (say from rain to wet streets or vice versa) are understood privatively: as enthymemes resulting from the suppression or hiding of one of the premises required for a proper warrant. Opposed to this might be a pragmatist line of thought, beginning with material inferences––that is, nonlogical, content-based reasoning. (Brandom, 1994: 101, emphasis added)

In early experimental psychology of reasoning, the nonmonotonic character of ordinary reasoning had been largely ignored or idealized away. In many recent approaches to reasoning, on the contrary, it has been given a central role. Some scholars, such as the cognitive scientist Keith Stenning and the logician Michiel van Lambalgen, aim to replace classical logic with a “nonmonotonic logic” that would provide better insight into the way people actually reason. Others, such as psychologists Mike Oaksford and Nick Chater, argue that reasoning is best viewed not as a logical but as a probabilistic–– and more specifically Bayesian––form of thinking.

The project of replacing standard logic with nonmonotonic logic or of replacing logic altogether with probabilities shares a basic presupposition with the traditional approach: that the study of inference must be based on a general and formal understanding of norms of good inference. We are not convinced. We have argued for an evolutionary and modularist view of inferential processes. Every inferential module aims at providing a specific kind of cognitive benefit, and at doing so in a cost- effective way. (Mercier and Sperber, 2017: 165)

We saw in ch. 3 (§4.1 and §4.2) that, in addition to sharing these connections, each theory contains valuable theoretical resources that the other lacks. M&S provide an empirical account

62 of reasoning that supports Brandom’s inferentialist theory of language, and the latter provides a conceptual framework that articulates in detail the socio-normative elements at the core of the interactionist theory. When combined, these views provide a substantive, systematic alternative to formalist theories of reasoning and rationality.

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