Stud. Hist. Phil. Sci. 34 (2003) 597–612 www.elsevier.com/locate/shpsa Epistemic divergence and the publicity of scientific methods Gualtiero Piccinini Department of Philosophy, Washington University, Campus Box 1073, One Brookings Dr., St Louis, MO 63130-4899, USA Received 20 May 2002; received in revised form 24 November 2002 Abstract Epistemic divergence occurs when different investigators give different answers to the same question using evidence-collecting methods that are not public. Without following the principle that scientific methods must be public, scientific communities risk epistemic divergence. I explicate the notion of public method and argue that, to avoid the risk of epistemic divergence, scientific communities should (and do) apply only methods that are public. 2003 Elsevier Ltd. All rights reserved. Keywords: Epistemic divergence; Public method; Intersubjective test; Reliabilism; Method of possible cases The activities of the sciences that are taught are things that can be seen and there is none that is not visible in one form or another. Hippocrates1 1. Introduction Scientific statements must be intersubjectively testable. If evidence for a statement cannot be obtained by different investigators, then neither the evidence nor the state- ment are scientific. Classical defenses of this principle have been given by Herbert E-mail address: [email protected] (G. Piccinini). 1 In The Science of Medicine, anciently attributed to Hippocrates. 0039-3681/$ - see front matter 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0039-3681(03)00049-9 598 G. Piccinini / Stud. Hist. Phil. Sci. 34 (2003) 597–612 Feigl (1953, p. 11), Carl Hempel (1952, p. 22), Immanuel Kant (1965, p. 645), and Karl Popper (1959, p. 44). In a stimulating paper, Alvin Goldman (1997) reformul- ates this venerable principle of scientific methodology as follows: Publicity principle: any method for collecting scientific evidence must be public. He argues that no notion of public method makes it plausible that public methods have better epistemic credentials than non-public ones; therefore, according to Gold- man, the publicity principle should be rejected (ibid., Sect. 3). For him, scientific statements need not be intersubjectively testable. Goldman’s challenge to this methodological pillar of modern science should be answered. By looking at motivations for the publicity principle and undesirable consequences of its rejection, this paper suggests a plausible explication of the notion of public method and good reasons to keep the publicity principle. In the next section, I’ll describe Goldman’s challenge in more detail. I’ll then apply Goldman’s proposal to a controversy over evidence-collecting methods and argue that some consequences of Goldman’s proposal are intolerable; hence, we should keep the publicity principle. In the following section, I’ll offer a modified definition of public method and defend it over Goldman’s. Finally, I’ll discuss different types of violations of the publicity principle and the epistemic problems they generate. That discussion shows how the publicity principle can be effectively applied to methodological disputes, reinforcing the conclusion that we should endorse it. 2. Goldman on public methods The principal topic of this inquiry is evidence-producing methods used by scien- tists within empirical scientific practices—what scientists usually describe in the methods section of their reports. In this context, here is Goldman’sdefinition of public methods: Method M is a public (intersubjective) evidence-producing method if and only if: (A) two or more investigators can severally apply M to the same questions, and (B) if different investigators were to apply M to the same questions, M would always (or usually) generate the same answers (induce the same beliefs) in those investigators. (Goldman, 1997, p. 534) A method that’s not public will be called private. Goldman notices that in (A) there is an ambiguity in the scope of can. According to a strong reading of (A), two investigators actually exist who can apply M to the same questions. This is implausible, says Goldman, for what happens if there is only one investigator? If a method is public when only two investigators remain, it should remain public after one of them dies. So, Goldman turns to a weak reading of (A), according to which it is possible that two investigators exist who apply M to the same questions. But then, he replies: G. Piccinini / Stud. Hist. Phil. Sci. 34 (2003) 597–612 599 [W]hy would the mere possibility that other creatures in an accessible world might apply the same method to the same question confer higher epistemic credentials on a belief? I detect no intuitive plausibility in this idea . Why must publicity be a necessary condition for evidence production? (Goldman, 1997, p. 537) Goldman doubts that a different definition of public method will add plausibility to the publicity principle (ibid., p. 537), and he urges his readers to reject the principle (ibid., p. 525). Goldman proposes replacing the publicity principle with two requirements inspired by his reliabilist epistemology. Goldman’s epistemological program is designed to account for knowledge in terms of the reliability of methods and processes by which beliefs are acquired, where a method or process is reliable if and only if it ‘leads to truth a sufficiently high percent of the time’ (Goldman, 1992, p. 129; see also Goldman, 1986, p. 27). Unless otherwise noted, I’ll use the term ‘reliability’ in Goldman’s sense. Epistemological reliabilism is not incompatible with the publicity principle: a reliabilist could still hold that scientific methods must be public. Gold- man, however, wants to dispense with the publicity principle in favour of two alterna- tive requirements, which methods must satisfy in order to be scientifically legitimate. First, a method must be reliable. Second, ‘a method should also satisfy a certain “negative” constraint, viz., that there not be (undefeated) evidence of its unreliability’ (Goldman, 1997, p. 543). A method that satisfies Goldman’s two requirements may or may not satisfy the publicity principle, and vice versa. One exception to this is that methods satisfying Goldman’s first requirement also satisfy clause (B): if a method M1 is reliable, and if different investigators apply M1 to the same question, then M1 will generally yield the same answer, namely the true one. Hence, if a method is reliable, it satisfies clause (B). But in general Goldman’s requirements and the publicity principle are orthogonal to one another. On one hand, a method M2 may be public but yield false results (violating Goldman’s first requirement), for example, because the experi- mental design doesn’t rule out certain defeating conditions or alternative expla- nations. If M2’s unreliability is discovered, M2 will violate both of Goldman’s requirements without ceasing to be a public method. Another method M3 might be deemed to be unreliable even though it is both public and reliable (violating Gold- man’s second but not his first requirement), for example, because the evidence that M3 is unreliable is flawed. On the other hand, a method M4 may be reliable but not public, for example, because only one individual endowed with unique cognitive abilities can apply M4 (violating clause (A)). The fact that the publicity principle and Goldman’s requirements are logically independent establishes that Goldman’s requirements are a genuine alternative to the publicity principle. For Goldman, then, a scientific method M need not be public, as long as M is reliable and investigators applying M have no evidence that M is unreliable. This proposal is not without consequences. In this paper, I will not dwell on reliabilism in epistemology: I will be as neutral as possible about the prospect of Goldman’s general program, which, as noted above, is compatible with maintaining the publicity principle. I will discuss only Goldman’s attempt to dispense with the publicity prin- 600 G. Piccinini / Stud. Hist. Phil. Sci. 34 (2003) 597–612 ciple in favor of his reliabilist requirements for legitimate scientific methods. I’ll argue that the publicity principle helps us evaluate the legitimacy of scientific methods in a way that Goldman’s proposed replacement does not. Hence, whether we are reliabilist epistemologists or not, we should keep the publicity principle. 3. Epistemic divergence and the publicity principle A community of investigators that gives up the publicity principle faces the risk of epistemic divergence. This occurs when different investigators answer the same question in different ways using private methods for collecting evidence. Disagree- ment leads to controversy, and in scientific controversies, researchers routinely critic- ize each others’ methods. In the absence of epistemic divergence, controversy is not a problem. To be sure, lack of epistemic divergence does not mean that investigators will easily reach agree- ment. Disagreements may be very hard to settle, for instance because different theor- etical commitments lead to different interpretations of the evidence. Also, agreement among investigators may or may not be good: if a community agrees on a false proposition, that may be epistemically undesirable. Avoiding epistemic divergence is no guarantee for agreement, and agreement is no guarantee for truth. But when methods are public, and hence there is no epistemic divergence, it is at least possible that disagreement and mutual criticism are a healthy component of the scientific dialectic, leading to improvements in methods and theories. In epistemic divergence, disagreement is a very different matter. When methods are private, the parties in the dispute share no means to prove that a method is flawed—they have no common epistemic ground on which to resolve their disagree- ment. As long as investigators are in epistemic divergence, their controversies can never be settled. Lack of epistemic divergence is thus a necessary condition for disagreement to be resolvable, or for agreement to be challenged with hopes that a new agreement will be reached.