Hume on Liberty and Necessity
by George Botterill
[***Note: This is a draft version of a paper whose final and definitive form was as published in: P. Millican ed., Reading Hume on Human Understanding, Clarendon Press: Oxford, 2002, pp.277-300.***]
Hume was certainly tackling a ‘long disputed question’ under his heading Of liberty and necessity. If our actions are causally determined, can we still maintain that we are capable of acting freely? Or does our deeply-rooted commitment to regarding other people as morally responsible agents also commit us to regarding them as exceptions to the general order of nature and, at some level, somehow exempt from the operation of causal laws? By now this has been disputed even longer, whether we call it the Problem of Free Will and (or versus) Determinism, or the topic of Moral Responsibility and Causal Determination. The basic issue is familiar enough to be referred to as an ‘old chestnut’ – which, in my view, implies we ought to have cracked it by now. Actually, I do believe that the position usually referred to nowadays as Compatibilism provides a solution to this problem, and no doubt this influences the view I take of Hume’s treatment of the topic. In order to relate Hume’s contribution to subsequent discussions and to the accumulated terminology of the debate, it will be useful to have a general scheme of the main positions in mind. Call the assumption that people – at any rate, normal adults – do have the capacity to act freely and are therefore morally responsible for their actions the Free Will Assumption. Evidently this is an assumption that we implicitly make in many different ways. For example, if a rottweiler attacks and injures a child, we may be shocked by the injuries and loathe and fear the dog that inflicted them. But we don’t blame the dog, because such an animal is not an appropriate target for that attitude: it cannot help the savagery which is part of its nature. And if the dog is put down, this is for reasons of safety, to prevent a repetition of the attack. It is not an execution. We take a different attitude to the dog’s owner, who should perhaps have foreseen the possibility of such an attack, and who in any case has a responsibility to control so dangerous a pet. What Hume calls ‘the doctrine of necessity’ is the Principle of Determinism, according to which all events (including all human actions) are entirely the result of prior causes. So now we go on to ask: can the Free Will Assumption and the Principle of Determinism both be true? That they can both be true, because they are logically consistent, is the answer given by Compatibilism. Those who hold that the Free Will Assumption and the Principle of Determinism cannot both be true are Incompatibilists. For these people there arises the further question: If they cannot, on grounds of logical consistency, both be true, which is false? Libertarians maintain that we have free will, and that we must therefore conclude that the Principle of Determinism is false, or at any rate does not apply to human actions and decisions. Hard Determinists maintain that the Principle of Determinism is true, and that therefore we are making a metaphysical error when we assume that people have free will. 2
Representing the general structure of the debate diagramatically, this is how the parties stand:
Can the Free Will Assumption and the Principle of Determinism both be true?
Answer: Yes Answer: No = COMPATIBILISM = INCOMPATIBILISM
So which is true? They are both true =
Answer: The Principle A nswer: The Free Will of Determinism Assumption = = HARD DETERMINISM LIBERTARIANISM
In discussions of free will and causal determination conducted outside the confines of academic philosophy compatibilism still remains little known and largely ignored. Indeed, non-philosophers and undergraduate beginners in philosophy seem to find compatibilism highly paradoxical, when first introduced to it. But within the history of philosophy the compatibilists can point to a dynasty of champions stretching from Hobbes through Hume to Ayer. For example, in one of his papers Donald Davidson announces that: "Hobbes, Locke, Hume, Moore, Schlick, Ayer, 3
Stevenson, and a host of others have done what can be done, or ought ever to have been needed, to remove the confusions that can make determinism seem to frustrate freedom."1 With such a tradition behind it, it is only natural to assume there has been some cumulative development in the compatibilist case, that it did not spring complete and perfectly formed from the head of Thomas Hobbes. In fact I think it is preferable to think of the case for compatibilism as composed of a battery of arguments, some much more forceful than others. Yet if one were looking for a single main argument that might be strengthened, the obvious and most popular candidate is one that derives from the thought that (i) the concept of freedom is contrastive, since there is a genuine distinction to be drawn between actions that are freely performed and those that are not, but that (ii) it is a mistake to suppose that the contrast is with causation in general. I shall refer to this argument as the Contrastive Argument.2 The tricky bit, of course, is to say exactly what it is that acting freely is to be contrasted with. The favoured options are the other three ‘C’s – coercion, compulsion, and constraint. How exactly we are to capture this contrast – between, on the one hand, cases in which people may be said to act freely, or voluntarily, or of their own free will and, on the other hand, cases in which they do not – is something that may still, after all these years, need a bit of working up. However, there is a presumption that a Humean account of causation cannot but be helpful to the Contrastive Argument, if only on the grounds that the less we pack into the general causal relation, the more will be available for the purposes of distinguishing those special causes that do frustrate the freedom of an agent. Whether or not a Humean account of causation aids the Contrastive Argument, I want to make it quite clear that Hume himself does not advance that argument. If we look carefully at what Hume says on this subject, we will hesitate to think of him as fitting into a single overall case for compatibilism based on the Contrastive Argument.3 That will be just as well, not only in order to report Hume’s position correctly, but also in order to appreciate the strength of the case for compatibilism. The biggest question is whether compatibilism provides a solution to the traditional problem of free will and determinism. Many philosophers have maintained that it does, and have acknowledged that Hume made an important, if not decisive, contribution to the development of compatibilism. So the further question arises: What exactly was the contribution that Hume made to compatibilism? In attempting to answer this question we need to look closely at the two places where Hume wrote about "liberty and necessity" in the Treatise and the first Enquiry. On reading through these passages we will observe that although they are in many respects closely similar, there is one striking difference between them. So we are led on to the further questions: What accounts for that striking difference? And is it more, or less,
1 From ‘Freedom to Act’ in Davidson (1980), p.63. 2 Its most influential statements have been Hobbes (1651), ch.XXI: "Liberty, or Freedome, signifieth (properly) the absence of Opposition ..."; Schlick (1939), p.150: "Freedom means the opposite of compulsion; a man is free if he does not act under compulsion, and he is compelled or unfree when he is hindered from without in the realization of his natural desires." ; and Ayer (1954), p.278: "For it is not, I think, causality that freedom is to be contrasted with, but constraint." 3 Paul Russell (1983) has also emphasised this point. In his (1988) he even argues that a regularity account of causation weakens the Contrastive Argument (which he calls the "compulsion argument"). 4 important than the similarities? I shall start with the last two questions, by analysing the similarities and differences between Hume’s two treatments. Section I describes the major difference between what Hume has to say on the topic in the Treatise and in the Enquiry. Sections II and III examine the similarities. In section IV I shall explain why it is a mistake to attribute the Contrastive Argument to Hume. Finally, in section V I will offer an evaluation of Hume’s contribution to the development of compatibilism.
I The Striking Difference The striking difference between Treatise II.III.I-II and Enquiry VIII is that in the former Hume is a partisan for the "doctrine of necessity" and against the "doctrine of liberty", whereas in the latter he presents himself as a peacemaker who will heal the breach between the two sides to this ancient dispute. In the Treatise he says that "there are always the same arguments against liberty or free-will" (p.407) and describes the doctrine of liberty as a "fantastical system" (p.404), as "absurd ... in one sense, and unintelligible in any other" (p.407), and as having "odious consequences" (p.412). His conclusion is that he "cannot doubt of an entire victory" – i.e., for necessity and against liberty. In sum, the author of the Treatise advises his readers plainly enough that there is no such thing as free will. Hume has become, by contrast, completely emollient in the Enquiry. After a couple of introductory paragraphs on the theme of how an apparently intractable controversy can be resolved if we will only avail ourselves of "a few intelligible definitions", he declares that "all men have ever agreed in the doctrine both of necessity and liberty" (p.81). He repeats this claim in what is perhaps the most frequently quoted passage of this section, where he describes his present discussion as a ‘reconciling project’: "But to proceed in this reconciling project with regard to the question of liberty; the most contentious question of metaphysics, the most contentious science; it will not require many words to prove, that all mankind have ever agreed in the doctrine of liberty as well as in that of necessity, and that the whole dispute, in this respect also, has been hitherto merely verbal." (p.95) To borrow the terminology introduced by William James, it would seem, then, that Hume was a hard determinist in the Treatise and a soft determinist in the Enquiry. However, although those categories are useful for some purposes, they are rather too crude to help us in the present case. In particular, hard determinism can come in different grades of toughness. The hardest form would insist that it is wrong to hold people accountable for their actions, and that moral attitudes to others based upon their supposed role as agents are all equally without any real foundation. It is clear that even in the Treatise Hume is not a hard determinist of that stamp. So in what does the reconciling softness of the first Enquiry consist? In order to assess the significance of the striking difference, we had better place it within the context of the similarities between THN II.III.I-II and EHU VIII. The similarities are extensive and involve the overall argumentative structure of the two passages. In both Hume divides the topic of "liberty and necessity" into two sections. In the first of these he attempts to establish that human conduct is no less the product of causal necessity than other events. In the second, he argues that, so far from causal necessity being inimical to morality, we need actions to be caused in order for moral sentiments to be directed upon their proper objects.
II The Doctrine of Necessity In comparing the two treatments of these two sections it seems appropriate to start, as Hume does, with his arguments for the doctrine of necessity (THN, pp.399-407; EHU, pp.82-94). It is here, in arguing the case for determinism, that Hume employs his new account of the idea of causal necessity. The point deserves emphasis: Hume uses his account of causation to argue that determinism is true of actions as well as other events, not in order to argue that determinism is compatible with actions being freely performed and justly subject to moral appraisal. In this respect his procedure is exactly the same in the Enquiry as in the Treatise. Moreover, when in the Abstract he (if it is he, as I am presuming it is) claims to have put "the whole controversy in a new light, by giving a new definition of necessity" he does not follow this up by claiming that we should now be able to see that there is no inconsistency between an action’s being caused and being freely performed. Instead, he immediately proceeds to explain that what must be accepted, even by "the most zealous advocates of free-will", is that actions exhibit causal necessity in his sense, because we know from experience that there are constant conjunctions between motives and actions, and because we do in fact confidently infer the latter from the former. He leaves to his opponents (the advocates for free-will) what he takes to be the impossible task of showing that there is anything more to causal necessity than constant conjunction and consequent inferential habits to be discovered in "the actions of matter". Since Hume reproduces in the Enquiry, with ingenious illustrative variation, the case he had made out for determinism in the Treatise, and since he had also advertised it in the Abstract as one of the philosophically useful results to be obtained from his definition of causation, we must judge that he was himself fairly well satisfied with his arguments for determinism. However, this part of his treatment of the topic of liberty and necessity cannot be described as having made a lasting contribution to the development of compatibilism, if only because a modern compatibilist need not be, as Hume was, a convinced determinist. Twentieth century science has certainly not delivered the unequivocal verdict in favour of determinism that appeared to be indicated by Newtonian mechanics. This, however, does not rob compatibilism of its philosophical interest. Perhaps we should preserve a cautious agnosticism on the speculative metaphysical issue of whether the universe is deterministic or not. So long as it is supposed that there is at least a possibility that determinism should be true, and in particular that human actions are causally determined, it will remain important to be able to show that this possibility would neither make our moral attitudes entirely groundless nor have the consequence that people could never justly be held responsible for what they have done. In fact, it would surely be very surprising (to put it mildly) if Hume, or anyone else, could establish the truth of determinism simply by appealing to our ordinary everyday experience of the world and of human conduct. Hume does not set himself this task in its full generality. In closely parallel passages in the two treatments he invites his readers to accept determinism with respect to the physical world as something that has already been established: "'Tis universally acknowledg'd, that the operations of external bodies are necessary, and that in the communication of their motion, in their attraction, and mutual cohesion, there are not the least traces of indifference or liberty." (THN, pp.399-400) "It is universally allowed that matter, in all its operations, is actuated by a necessary force, and that every natural effect is so precisely determined by the energy of its cause that no other effect, in such particular circumstances, could possibly have resulted from it." (EHU, p.82) 6
He therefore sets himself the slightly more modest objective of showing that we have much the same evidence for causal necessity with regard to motives and actions as we have with regard to events in the external material world and their causes. This is where the new definition of causal necessity is deployed. For, by Hume’s account of the twofold experiential root of our idea of necessity, such evidence can only consist in constant conjunctions between similar motives and similar actions, and an observer’s consequent disposition to infer actions from past experience of such regularities. In both treatments Hume concludes that experience does reveal constant conjunctions: "No union can be more constant and certain, than that of some actions with some motives and characters ..." (THN, p.404) "... the conjunction between motives and voluntary actions is as regular and uniform as that between the cause and effect in any part of nature ..." (EHU, p.88). There are, however, major problems concerning the claim of a constant conjunction between motives and actions. Hume is well aware of one of these, namely that it simply is not the case that experience manifestly reveals exceptionless regularities linking circumstances, character, and conduct: different people may react differently to the same circumstances, and a given individual may on occasion act out of character. A critic of the doctrine of necessity might feel entitled to point to this as contrary evidence. Hume formulates the objection pithily: "Necessity is regular and certain. Human conduct is irregular and uncertain. The one, therefore, proceeds not from the other." (THN, p.403). In the Treatise he devoted only about a page (pp.403-404) to explaining away this contrary evidence, and the guarded formulation of the conclusion cited above (in which he only claims a constant union "of some actions with some motives and characters") might indicate a degree of reservation as to whether he had actually succeeded in defeating the objection. He returned to the point in the Abstract, offering a memorable analogy designed to show that while psychological regularities are not invariably reliable they are no worse in this respect than other regularities: "Thirty grains of opium will kill any man that is not accustomed to it; tho' thirty grains of rhubarb will not always purge him. In like manner the fear of death will always make a man go twenty paces out of his road; tho' it will not always make him do a bad action." In the Enquiry the treatment of this difficulty is considerably expanded (pp.85- 88). The line Hume takes here is that any apparent exceptions to causal regularities should be attributed to undetected differences in the causes. While "the vulgar", on the one hand, attribute a lack of regularity "to such an uncertainty in the causes as makes the latter often fail of their usual influence" (p.86), on the other hand "philosophers" (I suppose we may take it that Hume means scientists) "form a maxim that the connexion between all causes and effects is equally necessary, and that its seeming uncertainty in some instances proceeds from the secret opposition of contrary causes" (p.87). There are several reasons why this method of explaining away apparent irregularity should raise the reader’s eyebrows. The first is that it is flatly inconsistent with what Hume claims at the beginning of Section VIII, namely that "all men have ever agreed in the doctrine both of necessity and of liberty" (p.81). For it now appears that the vulgar do not agree in the doctrine of necessity, at least not in regard to all actions, since such agreement depends upon a philosophical (or scientific) insight into 7 the possibility of "the secret operation of contrary causes". The second reason for unease is that Hume’s subsequent appeal to "this inference from motive to voluntary actions, from characters to conduct" (p.90) – the second requisite for our idea of causal necessity to be applicable to actions – is severely weakened. For we surely cannot be determined to form inferences by the secret operation of contrary causes, and yet awareness of this possibility ought to (and presumably would) weaken the confidence of any expectations concerning conduct in a rational student of human nature. The third reason for surprise at Hume’s way of defending determinism derives from the fact that THN II.III.I and EHU VIII come as close as Hume ever approached to redeeming the promissory note issued at the end of THN I.III.III, on Why a cause is always necessary. In that section Hume asserts that he has refuted the claim that it is either intuitively or demonstratively certain that "whatever has a beginning has also a cause of existence". One might have expected that Hume would then have proceeded to explain how belief in the causal principle is derived from experience. Instead he says "it will be more convenient to sink this question in" an examination of why we think that particular causes must have particular effects (THN, p.82). It sinks all right. The difficulty is to see whether it ever emerges again, except in the sections that we are now considering. Yet does he here show that experience alone either supports or induces a belief in universal causation? Hardly. When he says that "From the observation of several parallel instances, philosophers form a maxim that the connexion between all causes and effects is equally necessary" (EHU, p.87), this looks (in spite of the thin veil drawn by the first clause) very much like the active adoption of a regulative or methodological principle. It is actually an echo of the sixth of his rules by which to judge of causes and effects: "The difference in the effects of two resembling objects must proceed from that particular, in which they differ. For as like causes always produce like effects, when in any instance we find our expectations to be disappointed, we must conclude that this irregularity proceeds from some difference in the causes." (THN, p.174) But whatever the status of this rule might be4, its employment in the present case cannot be anything more than question-begging. Given that the issue is whether all actions are the result of antecedent causes, it cannot be admissible to argue that since they are effects they must therefore be the result of unknown causes, in any case in which they are not instances of a regularity manifest to experience. Our review of the way that Hume wrestles with this problem concerning the regularity of the connection between motives and actions is sufficient to show that he fails to make out a convincing case either for the claim that the doctrine of necessity applies to actions as to other events, or, for that matter, for the claim that everyone in practice assumes this to be so. But I implied above that there are other major objections to the alleged constant conjunction between actions and motives. It hardly needs to be remarked that the claim that an agent’s motives are causes of his actions has been the subject of a protracted controversy in modern analytical philosophy. I cannot enter into that controversy here, and hope I will not be accused of dogmatism if I restrict myself to observing that Hume’s view that motives are causes of action seems to me perfectly defensible and indeed correct.5 But there are three objections to the way Hume argues for the doctrine of necessity that we do need to consider.
4 For discussion of the puzzle as to how Hume could have thought that methodological rules were derived from experience see Passmore (1980), pp.52-60. 5 We might return the compliment on behalf of Hume et al. by saying that Davidson has removed the confusions that can make rationalization seem inconsistent with causation. 8
The first is that Hume’s procedure gives a very misleading impression as to how common sense psychology (often referred to by modern philosophers and psychologists as "folk psychology" or "theory of mind") actually works. Hume thinks that we arrive at expectations about conduct as a result of inferential habits formed by previously experienced regularities. Yet this could only be true if we started with an awareness of a person’s motives and then subsequently observed his actions. But how do we come to have beliefs about the motives of others? The answer must surely be: through interpreting their actions. In other words, the ascription of motives and reasons to agents is theory-laden: at least some part of the theory of mind (common sense psychology) must already be in place if we are ever to get started on the inter- connected projects of interpreting and predicting the actions of other human agents. An argument in the style of Chomsky that inductive learning (and thus, a fortiori, simple induction by repetition) is not sufficient to account for acquisition seems to apply with at least as much force to theory of mind as to linguistic competence.6 The second and third objections concern the point that Hume is in fact arguing for psychological determinism: that the doctrine of necessity applies to the connection between motives (internal states described in a psychological vocabulary) and actions. There are two difficulties here. The first (and, hence, second major objection to Hume’s procedure) is that in explaining away apparent failures of constant conjunction by appealing to unknown causes Hume offers no justification for the assumption that those unknown causes are psychological in character.7 It is doubtful whether any such justification can be provided and therefore doubtful whether psychological determinism is true. When two people with apparently similar motivation act in different ways, there is presumably some difference between them that accounts for this. But folk psychology is not a sufficiently tightly-knit and fundamental theory to ensure that such a difference must be capturable within its own explanatory and predictive resources. It could, for example, be the case that the crucial difference between these two people is a difference in the level of a certain hormone within their bodies, or a difference in the release of some neuro-transmitter within their brains. This point has implications for the second half of Hume’s argument. If determinism in general is true (i.e., if every event results from previous factors in accordance with exceptionless causal laws), but psychological determinism in particular is not, then the way an agent acts on a particular occasion may be due to some internal state without that internal state being part of the agent’s character. The third objection concerns the relevance, to the traditional problem of free will, of psychological determinism, in so far as such a determinism concentrates solely on psychological causes and their effects on action (the output side, as one might say). Hume does at times mention circumstances as well as character and conduct, but for the most part he maintains causal necessity in relation to action only in so far as the connection between motives and actions is concerned. An incompatibilist might well point out that it is not causal links that go back only as far as the psychological level that generate the problem of free will. For if determinism is true without restriction, then those psychological antecedents will have their
See D. Davidson 1963, ‘Actions, reasons, and causes’, Journal of Philosophy 60; also in Davidson (1980), pp.3-19. 6 See Carruthers (1992), chs.6-8, for the development of such an argument Also Botterill and Carruthers (1999), chs.3-4. 7 Mill (1843) makes the same assumption and equally fails to provide any justification for it. See A System of Logic, Bk.VI Ch.II.2. 9 necessitating causes in turn, and so we are driven back to acknowledge a causal origin for actions in events and states that lie outside the agent’s body and before his birth. Hence the ultimate causes of an agent’s actions are surely beyond his control, if determinism is true. Hume appears to confess, frankly and rather alarmingly, that he has no answer to this problem: "I pretend not to have obviated or removed all objections to this theory ... It may be said, for instance, that, if voluntary actions be subjected to the same laws of necessity with the operations of matter, there is a continued chain of necessary causes, pre- ordained and pre-determined, reaching from the original cause of all to every single volition of every human creature. No contingency anywhere in the universe; no indifference; no liberty. While we act, we are, at the same time, acted upon." (EHU, p.99) He proceeds to convert this into a theological discussion on whether God is responsible for all wrongdoing. But he should have seen that the problem is more general than that, and that the objection needs to be met, whether or not God is supposed the first cause of everything.
III Morality requires Necessity Hume’s overall strategy is to argue (1) that determinism is true, but (2) that this, so far from making attributions of responsibility problematic, is actually a precondition for moral sentiments to be directed towards their proper objects. We have seen that the first half of his case turns out to be an unconvincing, and indeed misconceived, attempt to establish the truth of psychological determinism. We have also noted that a compatibilist need not be convinced of the truth of determinism: in other words, that while a compatibilist must of course not be a hard determinist, he need not be a soft determinist either. So it is the second half of Hume’s position (to be found in THN, pp.407-412 and EHU, pp.96-103) that promises to be of more lasting relevance to the development of compatibilism. And in fact what Hume says here has often been re- worked and re-presented.8 In reading Hume’s two presentations of the second half of his case one can hardly fail to notice that in the Enquiry he has greatly improved the organization of his material. For in the Treatise the important argument that attributions of responsibility require us to see actions as causally determined by motives figures most awkwardly as the response to the third of three reasons "for the prevalence of the doctrine of liberty". The first two reasons both concern the relevance of introspection to the debate. They are: (1) that we are reluctant to allow that our own actions have been "govern'd by necessity", and (2) that "there is a false sensation or experience even of the liberty of indifference; which is regarded as an argument for its real existence." In part the reorganization of his material is forced on Hume by "the reconciling project". Whereas in the Treatise he was arguing for the doctrine of necessity and against the doctrine of liberty, in the Enquiry he is arguing that both are true, so he will hardly want to begin part II of Section VIII by explaining why we are
8 Two well-known and influential examples are Schlick (1939), pp.151-154 and Hobart (1934). Hobart’s summary of his main thesis would serve equally well as an epitome of the second half of Hume’s case: "absence of determination, if and so far as it exists, is no gain to freedom, but sheer loss of it; no advantage to the moral life, but blank subtraction from it." 10 mistakenly attached to the doctrine of liberty. But, of course, I hope it will by now have become clear that the phrase "the doctrine of liberty" does not bear the same meaning in the Enquiry as it did in the Treatise. In the Treatise "the doctrine of liberty" is a metaphysical position. It is what would nowadays be referred to as Libertarianism – the view that human agents have a contra-causal freedom of the will. Hume never resiles from his opposition to this position, but in the Enquiry he is quite happy to join with others in subscribing to "the doctrine of liberty", according to all that anyone can actually succeed in referring to when talking of the liberty involved in agency. This he defines as "a power of acting or not acting, according to the determinations of the will" (p.95), and of course in this formulation the phrase "the determinations of the will" is to be taken in a passive as well as an active sense. He intends it to be understood that the will is just as much determined as determining, that it is a causal intermediary between motives and actions. But, quite apart from this shift in usage of the phrase "the doctrine of liberty", it was rather careless in the Treatise to lump together the three reasons for the prevalence of the doctrine. For the first two reasons both invoked alleged introspective evidence against psychological determinism. So in the Enquiry he is quite right to relocate their treatment to a footnote to the first half of the case in part I of Section VIII (p.94). We come now to what had appeared in the Treatise as the third reason for the prevalence of the doctrine of liberty, which is rightly elevated in the Enquiry to the status of the focal point for the discussion of Section VIII part II. This is the charge that determinism (the doctrine of necessity) is subversive of religion and morality. He enters verbatim exactly the same protest in both treatments against any attempt to refute a hypothesis by appealing to "its dangerous consequences to religion and morality": "When any opinion leads to absurdities, it is certainly false; but it is not certain that an opinion is false, because it is of dangerous consequence. Such topics, therefore, ought entirely to be forborne; as serving nothing to the discovery of truth, but only to make the person of an antagonist odious." (EHU, p.96; there are only minor stylistic changes from the parallel passage in THN, p.409) Nevertheless, Hume is ready to meet this challenge because he believes he can show that the doctrine of necessity is "not only consistent with morality", but even "absolutely essential to its support" (EHU, p.97). In the Treatise he had claimed that "the doctrine of necessity, according to my explication of it, is not only innocent, but even advantageous to religion and morality" (THN, p.409). It is interesting, and surely significant, that in the Enquiry he no longer pretends that determinism is "advantageous to religion". Indeed, the final five paragraphs of Section VIII should surely tend to make the reader think that, if we are to accept the doctrine of necessity, then the existence of evil is a very severe problem for Christian belief. Hume camouflages this conclusion with a final paragraph which is a very masterpiece of ironic disingenuity. Admitting that he cannot explain "how the Deity can be the mediate cause of all the actions of men, without being the author of sin and moral turpitude", he makes a show of conceding that "[T]hese are mysteries, which mere natural and unassisted reason is very unfit to handle" and that philosophy should be "sensible of her temerity, when she pries into these sublime mysteries" (EHU, p.103). The camouflage is so flamboyantly disingenuous that we are left in no real doubt that Hume was more concerned that his real opinion on the subject should be discernible to the unprejudiced reader, than that he should escape personal odium from those apt to complain of consequences dangerous to religion. 11
Our present concern, however, is not Hume’s views on religious belief, but rather how he argues for the contention that the doctrine of necessity is essential to the "support" of morality. The same argument is advanced, for the most part in the very same words, in the Treatise (pp.410-412) and in the Enquiry (pp.97-99). Actions in themselves may be "blameable", but a person is not "answerable" for them unless they proceed from something "in him that is durable and constant"9. In other words, Hume thinks that it is a necessary condition of moral responsibility for anything that has been done that the actions should be attributable to "some cause in the character and disposition of the person who performed them". He advances the following considerations, which may be taken as counting either in favour of the view that this is a necessary condition for moral responsibility, or alternatively as evidence that people do in practice subscribe to this view: (1) People are not blamed for actions performed ignorantly and casually, "because the principles of these actions are only momentary, and terminate in them alone". Presumably, Hume’s thought is that in such cases we realise that if the agent were better informed he would act otherwise, and therefore the actions do not reveal anything blameworthy in his character. (2) People are less blamed for hasty and unpremeditated than for deliberated actions, because a hasty temper "infects not the whole character". (3) People are not blamed for something they have done once they have repented and reformed, because "actions render a person criminal merely as they are proofs of criminal principles in the mind" and after genuine repentance and reform the objectionable principles of conduct are no longer present. Paul Russell has urged10 that we should interpret Hume’s argument here in a "naturalistic" way. His claim is that Hume’s thesis is that it is a matter of psychological fact that the moral sentiments of approval and disapproval are only aroused in us by persons or their characters. Regarding a person as morally responsible is, therefore, a matter of our feelings with regard to his character. Knowledge of character, however, requires inference from actions to motives, and such inference in turn requires causal necessity. The conclusion is that "it is an empirical psychological fact that without necessity morality would be impossible" (Russell (1983), p.599). This cannot be quite right, since the psychological fact must be, not that characters directly arouse our moral sentiments, but rather that our beliefs about them do. So it would not be psychologically impossible for people to hold the moral attitudes involved in regarding others as responsible agents if beliefs about character failed to constitute knowledge, because they failed to track any genuine causal connections between actions and persistent internal states of the agent. If, however, that really were the case, then morality would certainly be ill-founded, because it would be based upon false and unreliable beliefs about people’s characters. That conclusion is quite sufficient to vindicate Hume’s contention that the doctrine of necessity is essential to the support of morality.
9 We can only wonder how Hume might have thought he could reconcile this with his celebrated pronouncement that persons are "nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement" (THN, p.252). Lacking, as he confessed in the Appendix to the Treatise, any satisfactory account of "the principles, that unite our successive perceptions in our thought or consciousness" (p.636), it was prudent of Hume not to re-open the discussion of personal identity in the Enquiry. 10 Russell (1983), especially pp.596-599. 12
Hume, of course, does not think that we should seriously entertain the nightmarish possibility of a general mismatch between our beliefs about character and the actual origins of conduct. For he has already remarked that by "liberty" we "cannot surely mean that actions have so little connexion with motives, inclinations, and circumstances, that one does not follow with a certain degree of uniformity from the other, and that one affords no inference by which we can conclude the existence of the other." (EHU, p.95) What we need to be clear about in relation to EHU VIII Part II is the question whether Hume’s account of causation plays any essential role in his argument that causal necessity is essential to the support of morality. He does begin (p.97) by recapitulating his claim that necessity "consists either in the constant conjunction of like objects, or in the inference of the understanding from one object to another". Hume thought this was a correct account of causal necessity, and, after all, there were then no rival accounts of causation as an instance of general law-like connection that he could have been expected to introduce into the discussion. So it is understandable that he should have thought it a unique distinction of his view of causation that it enabled him to explain how our beliefs about causation enter into our moral thinking and the formation of our sentiments towards other agents. However, all he actually does in Part II of Section VIII is to point out that we believe in the causal efficacy of rewards and punishments and that we depend on causal inference in attributing responsibility for an action to an agent. Any account of causation that (i) takes particular causal relations to be instances of general law-like connections, (ii) allows inference from effect to cause on the basis of knowledge of causal generalizations, and (iii) represents causes as of such a kind that psychological states can enter into causal relations with actions, would serve equally well. You do not need to be a Humean about causation – except in the loose sense that all those who accept the nomological character of causality are Humeans – in order to appreciate the force of Hume’s arguments in Enquiry VIII Part II.
IV The Contrastive Argument and the Three Liberties Most commentators attribute the Contrastive Argument to Hume. One way of doing so is by concentrating on the confusion that he alleges between "the liberty of spontaneity" and "the liberty of indifference", because the latter involves contra- causal freedom of the will whereas the former only requires that the agent should encounter no hindrance in doing what he wants to do.11 Penelhum, for example, describes this diagnosis of a confusion as "the major argument" and explains that liberty of spontaneity "is not opposed to the existence of causes, but is opposed to ‘violence’", and that, therefore, according to Hume: "[T]o be free is not to be prevented from doing that which you choose to do."12 Ardal gives a similar summary of Hume’s compatibilism: "When we remember that all the necessity involved in the causal relation belongs to the mind thinking about or observing sequences, one may see that, to Hume, causal
11 This, at least, is all that I think these two pieces of technical terminology are doing. Beyond that they hardly serve to introduce any additional clarity or precision to the debate, and in so far as they may suggest that there are only two kinds of "liberty" that are relevant to the discussion they are positively mischievous. 12 Penelhum (1974), p.120. 13 necessity would not, in any sense, restrict human freedom. It is because people have held erroneous views about necessity that they have failed to realize this. The error stems from confusing liberty of spontaneity and liberty of indifference. The first has as its opposite violence, the second has as its opposite necessity and causes."13 Moritz Schlick credits Hume with having been "especially clear" on the point that "morality is interested only" in freedom of conduct, not in freedom of the will. He goes on to add: "And this is quite correct. Freedom means the opposite of compulsion; a man is free if he does not act under compulsion, and he is compelled or unfree when he is hindered from without in the realization of his natural desires."14 Barry Stroud does at least notice that Hume does not repeat in the Enquiry the Treatise’s allegation concerning a confusion between the liberty of indifference and the liberty of spontaneity. But he does claim that in the Enquiry: "The ‘liberty of spontaneity’ is said to be the only kind there is." This claim carries a substantial load of interpretation, since Hume does not once use the phrase "liberty of spontaneity" in Enquiry VIII. Stroud presumes that Hume’s statement that by liberty we can only mean "a power of acting or not acting, according to the determinations of the will" is intended to express the liberty of spontaneity, which he now sees as the only intelligible idea of liberty. I suppose this might be taken as a characterization of the liberty of spontaneity. But whether it is or not is indeed a merely verbal issue concerning the definition of a piece of scholastic terminology. What is of real importance is that an agent may possess such a power of acting even when he acts under compulsion. Stroud takes this to be a defect in Hume’s account of liberty: "it can hardly be described as a subtle or profound analysis of the concept. A man from whom money is demanded with a gun at his head certainly has ‘a power of acting or not acting, according to the determinations of the will’. If he chooses not to give the money, he may, and if he chooses to give it, he may. The penalties will be much greater on the one alternative than on the other, but which alternative is realized now depends on his will. So this example would seem to count as a case of liberty, given Hume’s explanation of it, although it is clearly a case in which the kind of liberty Hume says it most concerns us to preserve is absent."15 The point is intended as a criticism of Hume’s treatment of liberty. Seen in a true light, it is no such thing. On the contrary, it is one of the strengths of Hume’s position that, since he does not rely on the Contrastive Argument, he can say of such a case of coercion that the agent has liberty, in one sense, and yet lacks that liberty which "it concerns us most to preserve". There is a muddle here which badly needs to be cleaned up, if we are ever to arrive at a reasonable view as to whether a compatibilist solution to the problem of free will and determinism is possible – whether Hume’s reconciling project can be successfully completed. Hume himself avoids the muddle, but the different senses in which he uses the term "liberty" have certainly helped to entangle others. Schlick remarked that it was unfortunate that Hume used the same word in two different senses.16 In fact, it is absolutely vital to see that in the passages and commentaries we
13 Ardal (1989), p.87. 14 Schlick (1939), p.150. 15 Stroud (1977), pp.145-6. 16 The 1939 English translation actually says that it is "freedom" that is inappropriately used to signify both freedom of the will and freedom of conduct. 14 are considering "liberty" carries three different senses, which can be distinguished as follows: liberty1: is libertarian liberty. It is a contra-causal freedom of the will. Hume sometimes marks this sense of "liberty" by saying that it is "opposed to necessity". liberty2: is that in virtue of which a person is an agent in respect of what he does, and it is therefore a condition of responsibility. It is what is present in intentional action and absent in such things as hiccoughing and snoring. liberty3: is the absence of unwelcome restrictions affecting choice of action. It is what you have when you act without being subject to coercion, compulsion, or an influence that is resented. The dominant species of liberty3 is socio-political freedom, although it is also true that circumstances can compel you to do something you would otherwise prefer not to do. Liberty1 is the liberty of indifference. Hume has the same opinion about it in both the Treatise and the Enquiry: there is no such thing, and that is just as well because, if there were, then we would either be incapable of holding moral attitudes to others (at any rate, to others, qua agents), or else if we held them they would be based on false beliefs. It is liberty2 that he identifies as "a power of acting or not acting, according to the determinations of the will". It is the actualization of this power that makes someone an agent in respect of anything done, and so it is a necesary (though not sufficient) condition for moral responsibility. The power is realized in the causal influence of an agent’s character on his actions, and that is why the causal determination of action is a requisite for morality. What he referred to in the Treatise as "the liberty of spontaneity" (not altogether happily, as he seems to have realized in revising his treatment of the topic for the Enquiry) may be identified with liberty3. This is "that species of liberty, which it concerns us to preserve". It should be remarked that liberty3 is obviously a matter of degree, since what restricts our freedom in social and political life is the threat of some penalty consequent upon action or inaction, and threats can be more or less severe. The division of the three liberties enables us to highlight some of the major mistakes so often perpetrated in the free will debate. The Libertarian incompatibilist insists on identifying liberty1 with liberty2. This is quite definitely an error, for reasons we shall go into in our final section. That is a familiar enough theme. Yet the compatibilist who relies on the Contrastive Argument is also at fault. For that argument amounts to little more than the contention that liberty3 is not to be identified with liberty1. This is quite true, but it is also neither very interesting nor very enlightening, and the Libertarian is fully entitled to protest that it misses the whole point of his concern that the truth of determinism would make human beings nothing more than conduits through which causal forces operate. For it is just as serious a mistake to identify liberty3 with liberty2, as it is to identify liberty1 with liberty2. Hume himself does not commit the mistake of identifying liberty3 with liberty2, though his text does not assist the reader to distinguish them. But notice this significant point: it would be completely fatuous to describe liberty2 as "even the most common sense of the word" or the sort of liberty "which it concerns us to preserve", as Hume describes the liberty of spontaneity (here liberty3) at THN pp.407- 8. In the first place, so far from it being a common sense of the word, there is no ordinary English word for liberty2. We could call it genuine agency, or intentional agency, or moral agency, but those are all philosophical coinage.17 Secondly, we are
17 This absence of a substantive should not be supposed to prevent us from talking or thinking about liberty2. We talk about its presence or absence on particular occasions 15 not concerned to preserve it. This is not because it is unimportant to us, but rather because we are in little danger of losing it, so long as we continue to live, unless some extraordinary and incapacitating calamity befalls, such as total paralysis or being transformed into a zombie. As Hume says, "this hypothetical liberty is universally allowed to belong to every one who is not a prisoner and in chains" (EHU, p.95). Strictly speaking, even a prisoner in chains still possesses liberty2 so long as he retains the power to rattle his chains or not, as he thinks fit. Yet the example (like that of someone in a straitjacket) is apt in so far as it comes as close as possible to providing an imaginable case of losing liberty2 while still remaining a person. It is crucial here to observe the distinction between compulsion and constraint18, and indeed even between two different kinds of constraint. If I am constrained to do something, then I am forced or obliged to do it, and so I act, though in a way I would prefer not to in the absence of the constraint. But if I am being held under constraint, then I am being prevented from acting – e.g., by someone sitting on top of me, or pinning my arms behind my back. A severe and lasting form of constraint, such as being closely confined, shackled, or put in a straitjacket, would still leave an agent with liberty2, but only as a potential which the unfortunate agent has no (or very little) opportunity to exercise. I think there can be little doubt that this was what Hume had in mind when writing of a liberty "universally allowed to belong to every one" who is not both a prisoner and in chains. Hume does not say – please note – that this is a liberty allowed to belong to every one except when compelled or coerced to act in a way they would rather not. He does well not to, for those who say it fail to discern the difference between liberty2 and liberty3, and in consequence confound the question of whether an agent is responsible with the question of whether he acts freely. Consider, for example, Ayer’s influential discussion of the topic: "If I am constrained, I do not act freely. But in what circumstances can I legitimately be said to be constrained? An obvious instance is the case in which I am compelled by another person to do what he wants. In a case of this sort the compulsion need not be such as to deprive one of the power of choice. ... Thus, if the man points a pistol at my head I may still choose to disobey him: but this does not prevent its being true that if I do fall in with his wishes he can legitimately be said to have compelled me. And if the circumstances are such that no reasonable person would be expected to choose the other alternative, then the action that I am made to do is not one for which I am held to be morally responsible."19 Ayer is accurate on the question of choice. We might say the bank clerk with a gun at his head had no choice, but chose the lesser evil. This sounds paradoxical, but in fact is not. The appearance of paradox derives from the fact that when we say we have "no choice but to ..." what we usually mean is that we do have a choice but that it is quite clear what choice we ought to make. "No choice" is like "no contest". What is "no contest" is not something that is not a contest: it is, rather, a contest that is very one-sided.
through descriptions of actions as voluntary or involuntary, intentional or unintentional, deliberate or accidental. 18 This is one of the reasons why I find it advisable to introduce the label "the Contrastive Argument". Some writers call it "the compulsion argument", others "the constraint argument". 19 Ayer (1954), p.279. 16
But what Ayer says about responsibility (in a case of someone acting under this sort of compulsion) is much less satisfactory. He makes it sound as if the poor clerk with a gun at his head is let off because we all yield to that sort of "persuasion". We can all agree that in this situation the clerk is not to be blamed for handing over the money. A manager who blamed the clerk for having done this would be more than (and worse than) stern and exacting. However, this is not because the clerk was not morally responsible for handing over the money, but rather because he did not do anything wrong. Faced with a choice of two evils he quite rightly chose the lesser evil. We can see this by altering the case in such a way that the lesser evil becomes the greater evil. Make the robber a terrorist and the subject of his demand something more dangerous than money, such as nerve-gas or plutonium. In that case one really does need to enter the plea, on behalf of the victim of coercion, that few of us would be courageous enough to refuse to comply.20 Aristotle seems to have discerned the correct view of this sort of case when he said that such actions (done from fear of greater evils) are mixed, but are more like voluntary actions.21 In spite of the horrible threat the agent still acts intentionally. It is quite obvious that his reason for complying is to avoid the threat being carried out. So what the agent does has the sort of causal origin that is required for responsible agency. But, equally obviously, this is the sort of case in which liberty3 is severely impaired. The conclusion to be drawn is that the Contrastive Argument is at best a digression from what ought to be the main focus of debate. For all it can show is that it is the presence or absence of compulsion or coercion, rather than causation in itself, that is relevant to the question whether an agent acts freely or not. But it is not whether an agent acts freely, in the sense of having liberty3, that is at issue in concerns over the implications of determinism for morality, but whether anyone can ever have genuine responsibility for their actions. Lest I be suspected of concocting an interpretation to suit my own purposes, it would be desirable to substantiate the claim that "liberty" occurs in each of these three senses in Hume’s text. The job is easy enough as far as liberty1 is concerned. I think it will be readily accepted that when Hume inveighs against "the doctrine of liberty" in Treatise II.III.I-II, it is liberty1 that he has in mind. This is proved by the way he summarizes his argument against the doctrine: "liberty, by removing necessity, removes also causes, and is the very same thing with chance. As chance is commonly thought to imply a contradiction, and is at least directly contrary to experience, there are always the same arguments against liberty or free-will." (THN, p.407) Throughout Enquiry VIII Hume is careful to avoid using "liberty" in the sense of liberty1, except in the footnote to p.94 (which reproduces nearly verbatim a paragraph on pp.408-9 of the Treatise), where he writes: "The prevalence of the doctrine of liberty may be accounted for, from another cause, viz. a false sensation or seeming experience which we have, or may have, of liberty or indifference ... liberty, when opposed to necessity, is nothing but the want of that determination, and a certain looseness or indifference ... And it seems certain, that, however we may imagine we feel a liberty within ourselves, a spectator can commonly infer our actions from our motives and
20 Galen Strawson makes much the same point about this sort of case (see Strawson (1986), p.396). He thinks it shows that according to "standard compatibilist accounts of freedom" one acts freely whenever one acts at all. So much the worse for the standard accounts. A more discriminating compatibilism will maintain that whenever one genuinely acts one has liberty2, but one may not have liberty3. 21 Nicomachean Ethics, Bk.III, 1110a-b. 17 character ..." Here, without doubt, "liberty" means liberty1. The one other use of "liberty" to mean liberty1 in Enquiry VIII also comes on p.96, and Hume marks the fact that he is there using the term in a special sense: "liberty, when opposed to necessity, not to constraint, is the same thing with chance; which is universally allowed to have no existence." It is more difficult to detail occurrences of "liberty" in the senses of liberty2 and liberty3 in an uncontroversial way. This is because, if my interpretation is right, when Hume uses "liberty" in Enquiry VIII he usually means liberty2, and has little to say about liberty3. Yet commentators who cannot resist acribing the Contrastive Argument to Hume generally fail to distinguish liberty2 from liberty3. The one exception seems to be Stroud who, as we have seen, mistakenly reproaches Hume for so defining liberty as to include cases in which liberty3 is impaired. So I will instead try to show that passages in which Hume may be thought to be advancing some form of the Contrastive Argument do not in fact support this interpretation. What textual evidence is there for ascribing the Contrastive Argument to Hume? It is slender indeed and consists in the following two passages:
A: “Few are capable of distinguishing betwixt the liberty of spontaneity, as it is call'd in the schools, and the liberty of indifference; betwixt that which is oppos'd to violence, and that which means a negation of necessity and causes. The first is even the most common sense of the word; and as 'tis only that species of liberty, which it concerns us to preserve, our thoughts have been principally turned towards it, and have almost universally confounded it with the other.” THN pp.407-8
B: “It will be equally easy to prove, and from the same arguments, that liberty, according to that definition above mentioned, in which all men agree, is also essential to morality, and that no human actions, where it is wanting, are susceptible of any moral qualities, or can be the objects either of approbation or dislike. For as actions are objects of our moral sentiment, so far only as they are indications of the internal character, passions, and affections; it is impossible that they can give rise either to praise or blame, where they proceed not from these principles, but are derived altogether from external violence.” EHU p.99
Much has been made of passage A and its contrast between the liberty of spontaneity and the liberty of indifference. Yet it should be noted that this passage occurs only in the Treatise. Though he repeats many of the arguments of the earlier version almost word for word in Enquiry VIII, this is not one of them.22 I have already pointed out that Hume could hardly have thought that liberty as defined (at EHU, p.95) as a power of acting or not acting, according to the determinations of the will was "that species of liberty, which it concerns us to preserve", and so "liberty of spontaneity" seems here to mean liberty3. There is one further, and quite decisive, consideration. This is that passage A cannot justly be taken as part of Hume’s "reconciling project". Quite apart from the fact that Hume did not conceive himself to be engaged in a reconciling project in the Treatise (the striking difference), the actual context in which passage A occurs is one in which he is anwering a possible objection
22 What he does instead (at EHU, pp.92-3) is to give a fuller and less misleading explanation of why the fact that we do not in acting feel any necessary connexion between motives and actions is, on his view of causal necessity, no objection to the doctrine of necessity. 18 to the doctrine of necessity. He is not arguing for compatibilism, but defending determinism against assault from alleged deliverances of introspection. The sentence which precedes passage A makes this clear enough: “After we have perform'd any actions; tho' we confess we were influenc'd by particular views and motives; 'tis difficult for us to perswade ourselves we were govern'd by necessity, and that 'twas utterly impossible for us to have acted otherwise; the idea of necessity seeming to imply something of force, and violence, and constraint, of which we are not sensible.” His point is simply that the fact that we have no phenomenological awareness of internal compulsion when we act does not count against the doctrine of necessity. So passage A is part of the case for maintaining that determinism is true, whether or not the truth of determinism is consistent with (or, as he subsequently argues, even required for) our attributions of responsibility. Passage B is certainly part of Hume’s contribution to the reconciling project. But it is only the final clause of this passage that could be seen as expressing a version of the Contrastive Argument, and that would be putting the emphasis in the wrong place. Moreover, if Hume were here committed to the Contrastive Argument he would have to mean that actions "derived altogether from external violence" were actions performed through fear of external violence. But this is not what he says, and we must surely credit him with being astute enough to distinguish between violent external causes and the threat of violence. He would, of course, be aware that Hobbes had maintained that fear and liberty were consistent. Besides, Hume would be the last person to overlook that our "internal character, passions, and affections" are implicated in our fear of violence and personal injury.
V Hume's Contribution to Compatibilism I conclude that it is a mistake to ascribe the Contrastive Argument to Hume. The idea of a unified Hume-Schlick-Ayer line on compatibilism is, therefore, a myth, since Schlick and Ayer clearly do rely on the Contrastive Argument. In doing so they skew the focus of the discussion, since they are concentrating on the distinction between acting freely and not acting freely (liberty3), and that is not a distinction fundamental enough to give us insight into what an agent’s responsibility for his actions consists in. Freedom may be a negative concept, but what distinguishes us as moral agents must reside in some positive power that we possess. Otherwise it would be difficult to explain why the Free Will Assumption applies to human beings and not to members of other species. Hume, however, has what is of central importance clearly in focus in both Enquiry VIII Part II and Treatise II.III.II. It must be admitted that his discussion of moral responsibility is too brief and sketchy to give full satisfaction. For example, the suggestion that it is really always an agent’s character that is the object of our moral sentiments should be questioned, since we can blame a person of generally good character for an occasional misdeed. Also, the claim that "repentance wipes off every crime, if attended with a reformation of life and manners" is a wildly implausible view of human forgiveness. Yet it would be wrong to dwell too long on these points because what Hume was after was not a detailed account, but the basic necessary condition for responsibility. If we express that by saying that a person can only be responsible for what he does if his doing it is the result of an intentional state that can be attributed to him, we have the essence of Hume’s reconciling position on liberty 19 and necessity. And that part of Hume’s case seems to me every bit as secure as he confidently proclaimed it was. So Hume did succeed in showing that what it is about an agent in virtue of which he may be held responsible for his actions (liberty2, or intentional agency) is not only consistent with those actions being caused, but actually requires them to be caused – by psychological states of the agent. He did not, however, follow this up by showing that it is also consistent with a completely unrestricted determinism which applies to an agent’s motivational states not only as causes, but also as effects of prior causes. So he did not complete the reconciling project. Concentrating on the agent’s intentional states may help us to do that, since the principal reason for supposing determinism inconsistent with attributions of responsibility derives from the thought that if determinism is universally true, then it cannot be that an agent could ever have acted otherwise than he did. Now, it is arguable that the notion of possibility involved here ought to be epistemic,23 so that what is required for responsibility is not that the agent’s acting otherwise than he did be consistent with all previous history and the laws of nature, but rather consistent with information cognitively available to the agent at the time of acting. But since we are not here concerned with arguments Hume did not offer that might strengthen the case for compatibilism, this is not the place to pursue this line of thought further. It may now seem that the striking difference between the Enquiry and the Treatise is not really so important after all. In a way that is true, since the main argument for regarding the causal determination of action as essential to moral appraisal is the same in both sources (see section III above). However, in refusing to allow his Libertarian opponents a proprietary usage even of the word "liberty" he did see a very important point: "Whatever definition we may give of liberty, we should be careful to observe two requisite circumstances; first, that it be consistent with plain matter of fact; secondly, that it be consistent with itself." EHU, p.95 Hume thought that "liberty" in the sense of liberty1 – contra-causal Libertarian liberty – failed on both counts to be a permissible meaning of the word. Since we do not share Hume’s belief that the truth of determinism is "plain matter of fact" we cannot put the objection to Libertarianism in exactly the same way as he does. However, a slight amendment to Hume’s point, designed to accommodate agnosticism as to the truth of determinism, is sufficient to show why it is a mistake to identify liberty1 with liberty2, the liberty which grounds attributions of responsibility. For we cannot know an action, or any other event, to be uncaused. So we surely must not base our attributions of responsibility upon a contra-causal freedom that we can never in any single instance know that an agent possesses. My conclusion is that Hume’s contribution to compatibilism was not only very considerable, but also considerably better than has usually been thought. Although his rather casual and shifting usage of the term ‘liberty’ makes his discussion of the topic more difficult to follow than it need have been, his most important argument in both the Treatise and the Enquiry (the argument of THN pp.410-412 and EHU pp.97-99) is clearly directed at the fundamental issue of the conditions for responsible agency. Nor does he succumb to the tempting trap, into which many later compatibilists have fallen, of supposing that responsible agency is merely a matter of acting in the absence of coercion or constraint.
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23 Cf. Dennett (1984), p.148.