Canadian Journal of Philosophy Hume's Academic Scepticism: A Reappraisal of His Philosophy of Human Understanding Author(s): John P. Wright Reviewed work(s): Source: Canadian Journal of Philosophy, Vol. 16, No. 3 (Sep., 1986), pp. 407-435 Published by: Canadian Journal of Philosophy Stable URL: http://www.jstor.org/stable/40231479 . Accessed: 20/02/2012 12:28 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. Canadian Journal of Philosophy is collaborating with JSTOR to digitize, preserve and extend access to Canadian Journal of Philosophy. http://www.jstor.org CANADIAN JOURNAL OF PHILOSOPHY Volume 16, Number 3, September 1986, pp. 407-436 Humes Academic Scepticism: A Reappraisal of His Philosophy of Human Understanding JOHN P. WRIGHT University of Windsor Windsor, Ont. Canada N9B 3P4 A philosopher once wrote the following words: If I examine the PTOLOMAIC and COPERNICAN systems, I endeavour only, by my enquiries, to know the real situation of the planets; that is, in other words, I endeavour to give them, in my conception, the same relations, that they bear towards each other in the heavens. To this operation of the mind, therefore, there seems to be always a real, though often an unknown standard, in the nature of things; nor is truth or falsehood variable by the various apprehensions of mankind. Though all human race should for ever conclude, that the sun moves, and the earth remains at rest, the sun stirs not an inch from his place for all these reasonings; and such conclusions are eternally false and erroneous .1 1 David Hume, The Sceptic,' in The Philosophical Works of David Hume, 4 vols. ed. T.H. Green and T.H. Grose (London: 1892-96; reprinted by Aalen: Scientia Verlag 1964) Vol. 3, 217-18 407 John P. Wright The essence of the philosophical view expressed in this passage is very simple, but is, I believe, also very profound. The philosopher I have quoted claims, in the first place, that whatever is the case is what it is quite apart from human conceptions and beliefs. He expresses this view by saying that 'truth or falsehood' is not Variable by the various apprehensions of mankind/ He illustrates this view by the example of the Ptolomaic system: even if human beings had always reached the conclusion that the sun goes around the earth, that would in no way change the fact that that belief is false. The second claim made by the philosopher I have quoted is an epistemological one. He characterizes the attempts of astronomers to discover the real positions of the planets as an 'endeavour' to reproduce in their conception 'the same relations' that the planets have in reality. The philosopher presents this example as a model for all scientific enquiry. But he notes that it is 'often' the case that the real relations of things which we try to reproduce in our conceptions are based on an 'unknown standard.' In other words, human enquiry often proceeds without our having the ability to determine with any sort of certainty the relations of things in reality. Thus, the brief passage I have quoted gives not only a clear expression of a realist ontology, but also a suggestion of what may be called a sceptical epistemology. It is, I think, appropriate to give the label 'sceptical realism' to the overall philosophical view we find suggested here. The words I have just discussed were written by an eighteenthcentury philosopher by the name of David Hume. They occur in an essay called 'The Sceptic' which Hume published in 1742, three years after his first philosophical work, A Treatise of Human Nature.2 The essay is one of four in which Hume sought to describe 'the sentiments of sects, that naturally form themselves in the world, and entertain different ideas of human life and of happiness.'3 (The others are called 'The Platonist,' 'The Stoic,' and The Epicurean.') There are good reasons to think that the views expressed in 'The Sceptic' are those of Hume himself.4 The essay 2 David Hume, A Treatise of Human Nature, ed. L.A. Selby-Bigge, 2nd edition revised by P.H. Nidditch (Oxford: Clarendon Press 1978); hereafter referred to as Treatise, followed by the page number. 3 The Epicurean,' in Philosophical Works, Vol. 3, 197, n.l 4 The account of human happiness described in the essay is closely connected with some of the conclusions reached in Hume's letter to an unknown physician (The Letters of David Hume, 2 vols. ed. J.Y.T. Greig [Oxford: Clarendon Press 1932] Vol. 1, 12-18). In this remarkable document Hume records his own personal failure to live by the maxims of the Stoic philosophy. In 'The Sceptic' Hume 408 Hume's Academic Scepticism espouses a form of moral scepticism which there is every reason to think that Hume himself adopted.5 The specific passage which I have quoted argues, in the first place, that our 'affections' are of such 'a very delicate nature, and cannot be forced or constrained by the utmost art or industry.' Secondly, he argues that in curbing our 'vicious passions' such maxims would also extinguish 'such as are virtuous' and leave 'the mind totally indifferent and unactive' (224-5). 5 In a recent book, David Norton argues that Hume rejects 'ethical or moral scepticism ': the latter is defined as a view 'wherein the objectivity of moral distinctions is denied as a consequence of investigation into human motivation, belief, and action' (David Hume: Common-Sense Moralist, Sceptical Metaphysician [Princeton: Princeton University Press 1982), 244). It is difficult to know who, in Hume's time, held the view which Norton describes. Hume himself, at the beginning of his Enquiry Concerning the Principles of Morals, claims that those who deny the 'reality of moral distinctions' are entirely 'disingenuous' (Enquiries Concerning Human Understanding and Concerning the Principles of Morals, ed. L.A. Selby-Bigge, 3rd edition revised by P.H. Nidditch [Oxford: Clarendon Press 1975], 169). He himself opposes moral sceptics who have inferred that all moral distinctions arise from education but he goes on to argue that such a view (while not correct) is based on some genuine philosophical insights. Hume argues in opposition to the moral sceptic that 'any judicious enquirer' must admit that moral distinctions are 'founded on the original constitution of the mind.' Such an admission is made by those who think that virtue pleases 'either from considerations of self-interest, or from more generous motives and regards' (214-15; italics are mine). Norton's prime candidate for a moral sceptic is Hobbes. But Hume appears to recognize that Hobbes believed that moral distinctions are based in self-interest and are thus rooted in the original constitution of the human mind. For Hume criticizes Hobbes for holding an incorrect account of the original constitution of the mind. This is the upshot of his criticism of the Hobbist state of nature in the Enquiry Concerning the Principles of Morals (189). Moreover he argues that no man could ever behave in the manner of Hobbes' natural man (Treatise, 402). Hume's account of the Hobbist theory of benevolence is a bit peculiar (Enquiry Concerning ... Morals, 297), but at least it shows that Hume recognized that morality for Hobbes was based on an inference from the passions not on education. I can find no evidence that Hume thought of Hobbes as a moral sceptic. Hume himself is a moral sceptic in a traditional sense. The ethical views of the Academics grew out of their criticisms of the principles of the Stoics; the appeal to what is in some sense natural was important both for Sextus Empiricus and Carnaedes (see Sextus Empiricus, Outlines of Pyrrhonism, in Sextus Empiricus , 4 vols., trans. R.G. Bury [Cambridge, MA: Harvard University Press, 1961] Vol. 1, 17; Cicero, Academica, in Cicero, 28 vols. trans. H. Rackham [Cambridge, MA: Harvard University Press 1933] Vol. xix, 639). Hume adopted the view of the Academics, rather than the Pyrrhonists. Sextus notes that the former argue that 'it is more probable that what they call good is really good rather than the opposite, and so too in the case of evil, whereas when we [the 409 John P. Wright occurs in a section of the essay in which Hume supports this moral scepticism by the philosophical reflection that 'objects have absolutely no worth or value in themselves/ Rather, it is argued that value depends on 'the particular fabric or structure of the mind' (The Sceptic/ 218-19). The contrast which Hume makes here between moral and aesthetic judgments on the one hand, and scientific ones on the other, is fundamental in his philosophy and is repeated in his Enquiry Concerning the Principles of Morals. There he states that the standard of the former judgments lies in the 'peculiar nature' of the animal who makes them. However, our standard in science is 'founded on the nature of things' and is 'eternal and inflexible , even by the will of the Supreme Being/6 Hume's faith in the existence of an external world which is wholly independent of human belief will seem puzzling to many because he has so often been treated as a kind of cryptophenomenalist. For example, in Hume's Theory of the External World, H.H. Price asserted that Hume held the view that 'material objects consist entirely of "perceptions." '7 In this book and a well-known article entitled 'The Permanent Significance of Hume's Philosophy' Price provided a reconstruction of Hume's philosophy which attempted to expunge the sceptical elements.8 Hume's mistake, according to Price, was to retain an outdated conception of reason which left him thinking that our ordinary ways of determining causal relations were inadequate. Nevertheless, Price argued, Hume's philosophy could be reinterpreted so as to remove all talk of unknown standards. Other writers who have adopted Price's analysis have been less cautious in separating Hume's own views from those involved in the phenomenalist reconstruction of his philosophical thought. But the faith in an objective world which science seeks to discover also appears to be at odds with many interpretations of Hume as a sceptic . Richard Popkin has written that Hume, following Pierre Bayle, adopted a 'new Pyrrhonism a doubting of the real existence of everything, and an asserting that all that we could ever be acquainted Pyrrhonists] describe a thing as good or evil we do not add it as our opinion that what we assert is probable, but simply conform to life undogmatically that we may not be precluded from activity' (Sextus Empiricus, 139). 6 Enquiry Concerning the Principles of Morals, 294 7 H.H. Price, Hume's Theory of the External World (Oxford: Clarendon Press 1940), 223 8 H.H. Price, The Permanent Significance of Hume's Philosophy,' Philosophy 15 (1940), 7-37 410 Hume's Academic Scepticism with were mental appearances/9 Popkin elsewhere argues that the Humean sceptic 'believes whatever nature leads him to believe, no more and no less'10; but there is no reason to think that the belief in scientific objectivity expressed in The Sceptic' is merely a natural belief. Robert Fogelin has recently argued that Hume puts forward a 'theoretical skepticism' which is 'wholly unmitigated.' Fogelin maintains that Hume's only response to this Pyrrhonian scepticism is to show that it cannot be maintained in practice: 'we do not argue' to the mitigated scepticism which is adopted by Hume at the end of his Enquiry Concerning Human Understanding.11 If, as Fogelin implies, Hume had merely adopted a practical solution to sceptical doubts, this would hardly allow him to embrace the theoretical scientific realism which is espoused in the passages I have pointed out. In this paper I shall argue that the scepticism which Hume himself adopted requires a commitment to an objective world which is quite distinct from one which could be based on our perceptions. At the same time I shall argue that it is misleading to say that the Humean sceptic merely embraces beliefs which are imposed on us by human nature. The mitigated scepticism adopted by Hume himself involves a theory about the limits of human perceptions and the way that those limits are transcended by the suppositions which we all naturally make. I shall argue that, on Hume's view, these natural suppositions themselves provide the raw material for correct scientific judgment. I Pyrrhonism in Hume's philosophy Let me begin by considering the suggestion of Richard Popkin that Hume adopted a kind of new Pyrrhonism. It is helpful to consider carefully how Pyrrhonian scepticism emerges in his philosophy. The classical description of this scepticism was given by Sextus Empiricus in 9 R.H. Popkin, 'Berkeley and Pyrrhonism,' The Review of Metaphysics 5 (1951); reprinted in M. Burnyeat, ed., The Skeptical Tradition (Berkeley and Los Angeles: University of California Press 1983), 377-96, esp. 392. 10 R.H. Popkin, 'David Hume: His Pyrrhonism and his Critique of Pyrrhonism,' The Philosophical Quarterly 1 (1951); reprinted in V.C. Chappell, ed., Hume: a Collection of Critical Essays (New York: Doubleday 1966) 53-98, 95. 11 Robert Fogelin, 'The Tendency of Hume's Skepticism,' The Skeptical Tradition 397-412, esp. 399 & 410. 411 John P. Wright his Outlines of Pyrrhonism. Scepticism, according to Sextus, is 'an ability , or mental attitude, which opposes appearances to judgements in any way whatsoever, with the result that, owing to the equipollence of the objects and reasons thus opposed, we are brought firstly to a state of mental suspense and next to a state of "unperturbedness" or quietude/12 There are three elements involved in this initial description of scepticism: 1. the opposition between what appears (phenomena) and what is thought or judged (noumena); 2. the suspension of judgment (epoche); and 3. the state of tranquillity (ataraxia). This initial description becomes more complex when Sextus goes on to allow that phenomena might be brought into opposition with phenomena or noumena with noumena. There is also some dispute among scholars as to just what Sextus means when he refers to phenomena or appearances here. Myles Burnyeat has recently pointed out that Sextus goes on to say that by phenomenon or appearance he means 'the impression (phantasia) of the thing that appears / Thus there are also impressions (phantasiai) of other things such as thoughts.13 This in fact reflects Hume's own use of the term 'phaenomenon.' He employs the term sometimes to refer to the immediate contents of our senses (e.g., Treatise, 196, lines 14 & 29) and at other times to refer to the judgments we naturally make (e.g., Treatise, 256, line 26).14 In spite of these complications I believe that the most characteristic form of Pyrrhonian scepticism in Hume's philosophy may well be described in terms of the ability to oppose 'appearances to judgements.' We may reasonably identify the judgments with what Hume calls 'the sentiments of the vulgar' (Treatise, 223) or 'the reflections of common life.'15 In Hume's Treatise such natural judgments have their roots in that 12 Sextus Empiricus, 7 13 Myles Burnyeat, 'Can the Sceptic Live his Scepticism?' in M. Schofield, M. Burnyeat , J. Barnes, eds., Doubt and Dogmatism: Studies in Hellenistic Epistemology (Oxford: Clarendon Press 1980) 20-53, esp. 34. 14 In Hume's own day the term was used mainly in the context of natural philosophy for whatever requires explanation. Indeed this seems to be the sense in which Hume uses the term though his interest is mainly in moral rather than natural phenomena. I am indebted for these remarks to an unpublished paper by Mr. Tony Couture entitled 'A Study of Hume's Phaenomena in the Treatise.' 15 David Hume, Enquiry Concerning Human Understanding in Enquiries Concerning Human Understanding and Concerning the Principles of Morals, 3rd ed., ed. by L.A. Selby-Bigge, revised by P.H. Nidditch, (Oxford: Clarendon Press 1975), 412 Hume's Academic Scepticism faculty of mind which he calls imagination. An example of such a noumenon is the judgment of men who 'in their common and careless way of thinking ... imagine they perceive a connexion betwixt such objects as they have constantly found united together' (Treatise, 223). But this judgment is directly opposed to one we form on the basis of the way things actually appear to us on the basis of phenomena, if you will. Hume denies that we have any impression or idea of a connection between objects. Hume claims that our ideas of cause and effect are entirely distinct and that therefore we have no perception of a connection or power in any object.16 Thus our natural judgment that we have a direct perception of power in objects is directly opposed to the examination of what appears; this reveals that we have no such perception. In order to understand what Hume calls 'the force of the Pyrrhonian doubt' {Enquiry, 162) it is important to fully appreciate the claims which ideas or phenomena make on us. It is certainly true, as Hume's contemporary Thomas Reid maintained, that his scepticism is based on the development of the theory of ideas of his predecessors; however, Reid distorted that theory when he ascribed the view of ideas as entities to writers such as Descartes, Arnauld, and Locke.17 In its full generality the theory of ideas states that 'everything that is contained in the clear and distinct idea of a thing can truly be affirmed of that thing.'18 The essence of the theory lies in the claim that our knowledge of reality must be based on the analysis of our idea-contents.19 Hume's predecessors differed in their accounts of our clear and distinct ideas but he himself proposed to resolve their disputes by what is commonly called his empiricist prin162 ; hereafter this work will be referred to as Enquiry followed by the page number. 16 Treatise, 79-80; cf. Enquiry 30, 63. 17 See John W. Yolton, Perceptual Acquaintance from Descartes to Reid (Minneapolis : University of Minnesota Press 1984). 18 Antoine Arnauld et Pierre Nicole, La Logique ou L'Art de Penser (Paris: Flammarion 1970), 388: Tout ce qui est contenu dans l'idee claire & distincte d'une chose, se peut affirmer avec verite de cette chose.' This sentence is mistranslated in A. Arnauld, The Art of Thinking, trans. James Dickoff and Patricia James (Indianapolis : Bobbs-Merrill 1964), 320. 19 Hume thought that an examination of these contents would reveal that they do not give us any idea of 'independency' {Treatise, 191; cf . 194). But this is clearly not the view of Descartes or Locke. See John P. Wright, The Sceptical Realism of David Hume (Minneapolis: University of Minnesota Press 1983) 79-80, n.ll. 413 John P. Wright ciple. According to this principle, every meaningful term is based on an idea which has its source in some (internal or external) sense impression. Hume used this interpretation of the theory to argue that we lack ideas corresponding to the fundamental scientific notions of his day those of absolute space and time {Treatise, 64-5), causal power (Treatise, 155-72; Enquiry, 60-79), and matter (Treatise, 226-31; Enquiry, 154-5). But it is not only philosophical or scientific notions which Hume thinks that we cannot comprehend; our ordinary notions of external existence and causality are also quite incomprehensible. Thus, for example, Hume employs his principle to establish that we are only directly aware of fleeting perceptions which cease to exist when unperceived not external and independent objects. He uses the principle to establish that we only have ideas of contiguity, succession, and constant conjunction not of the power by which the cause produces its effect. What we mistake for such objective power is merely a subjective impression of the mind. The appeal of Hume's analysis of our sense-derived ideas has been so convincing that many have thought that his own ontology was based on his version of the theory of ideas. But Hume himself thought that these analyses led to nothing but Pyrrhonian doubt. In order to see this we must also appreciate the opposing claims of the noumena those of the reflections of common life. In his writings on the understanding, Hume identified certain suppositions which originate in that faculty of mind which he calls the imagination; in fact, we would be closer to the roots of Hume's own sceptical problem if we spoke of his theory of natural suppositions rather than (as is commonly done) of his theory of natural beliefs.20 Certain of these suppositions are clearly identified with our ordinary view of things. For example, Hume says that almost everyone, including philosophers in their daily lives, 'take their perceptions to be their only objects, and suppose, that the very being, which is intimately present to the mind, is the real body or material existence ' (Treatise, 206; italics are mine). This direct realism is elsewhere 20 For, strictly speaking, 'the idea of an object is an essential part of the belief of it . . .' {Treatise, 94) and we have in fact no proper idea of those objects we naturally suppose. However, Hume extends his account of belief to 'fictions' that is, to confused ideas; these fictions form the basis of our natural suppositions. Thus, for Hume, one can believe in external existence without having a clear idea of external existence; one of the clear ideas which enters into our natural supposition of external existence is enlivened and thus the fiction is believed {Treatise, 208-9; cf. Michael Williams, 'Hume's Criterion of Significance,' Canadian Journal of Philosophy 15 (1985), 273-304, esp. 283-4. 414 Hume's Academic Scepticism identified as that which the mind holds in its 'common situation' (Treatise, 213). Similarly Hume says that when 'the generality of mankind' experience the ordinary operations of nature they 'suppose that ... they perceive the very force or energy of the cause, by which it is connected with its effect' (Enquiry, 69; again, the italics are mine). These natural suppositions are directly opposed to what we discover on the basis of our sense-derived ideas. But, as we shall see, Hume thinks that they have some claim to give us a genuine account of reality. We can conclude therefore that Hume himself practices Pyrrhonian scepticism in so far as he opposes noumena and phenomena what we in ordinary life suppose to be the case and that for which we have direct evidence through our ideas. These are totally opposed and entail entirely different accounts of what really is the case. But what are we to say of Hume's view of the other two components of Pyrrhonism suspension of judgment (epoche) and tranquility (ataraxia)! Does Hume accept these two components of ancient Pyrrhonian scepticism? It seems quite clear, as Terence Penelhum has recently stressed, that he does not.21 The Pyrrhonian claims that he can live without belief, making no assertion about external things;22 but this is what Hume denies that we can do. Hume does allow that 'a Pyrrhonian may throw himself or others into a momentary amazement and confusion by his profound reasonings' but he denies that this condition can last any length of time.23 Hume denies the psychological validity of the Pyrrhonian sceptic's claim to withhold belief and judgment: 'Nature, by an absolute and uncontroulable necessity has determin'd us to judge as well as to breathe and feel' (Treatise, 183). Hume also claims that, even if such a state were capable of being achieved, it would not lead to tranquility or ataraxia. If the Pyrrhonists' principles were 'universally and steadily to prevail' then men would 'remain in a total lethargy, till the necessities of nature, unsatisfied, put an end to their miserable existence' (Enquiry, 160). Hume clearly did not see Pyrrhonism as the road to happiness as did its proponents. The fact that Hume rejects these aspects of Pyrrhonism is quite important . It indicates that whatever we might mean by calling Hume a 21 Terence Penelhum, God and Skepticism (Dordrecht: Reidel 1983), 124ff. 22 Sextus Empiricus, 11 23 Enquiry, 160; cf . Hume's description of the results of Berkeley's philosophy at Enquiry, 155. 415 John P. Wright sceptic, this does not mean that he is agnostic regarding our fundamental ontological suppositions.24 According to Hume, it is impossible to withhold belief about such matters as the existence of an external world or the belief in causal powers. At the same time the fact that Hume rejects the possibility of the Pyrrhonian suspension of judgment tells us less than is commonly thought about the nature of Hume's own scepticism. In acknowledging that nature forces us to judge, Hume certainly indicates some sort of accommodation with the appearances. But this clearly does not mean what Richard Popkin has said it means that the Humean sceptic believes only what nature leads him to believe. For Hume's Pyrrhonian sceptic stresses that even the most reliable of our natural instincts 'may be 24 In the final analysis this seems to be David Norton's interpretation of Hume's scepticism. According to Norton, Hume is said to be 'diffident about those beliefs' to which our natural propensities lead us {David Hume: Common-Sense Moralist, Sceptical Metaphysician, 202; cf . his 'Review of John P. Wright, The Sceptical Realism of David Hume,' Philosophical Books 25 [1984], 144-8). Norton argues that according to Hume one can actively challenge a belief to which one cannot be hesitantly disposed and thus doubt and not doubt at the same time {David Hume: Common-Sense Moralist, Sceptical Metaphysician, 288-9). The same view is espoused by Popkin in the article referred to in note 10 (95-6). But while Hume's academic sceptic is 'diffident' toward certain beliefs he is not diffident to those fundamental beliefs to which our natural propensities lead us. It would be a mistake to interpret Hume as recommending in the last section of the Enquiry (161ff.) that we be hesitant in accepting beliefs such as the basic beliefs in causal connection or external existence. In his A Letter from a Gentleman to his Friend in Edinburgh (Edinburgh, 1745; reprinted with an introduction by E.C. Mossner and J.V. Price [Edinburgh: Edinburgh University Press 1967]), Hume wrote that 'a Philosopher who affects to doubt of the Maxims of common Reason, and even of his Senses, declares sufficiently that he is not in earnest...' (19). I believe that the doubting activity, which Norton in fact reduces to a mental disposition, should be identified with the activity of reason: for reason is capable of discovering the falsity of certain aspects of those beliefs which we hold on the basis of a natural propensity. Reason shows us that we lack evidence for our natural suppositions. It is true that Hume sometimes suggests that such reflection briefly leads us to a complete suspension of judgment. Thus, as Penelhum points out, in characterizing the results of his inquiries Hume describes himself as being 'hesitant and dogmatic by turns' {God and Skepticism, 124). But the point I wish to make is that this does not represent the final position on scepticism either in the Treatise or the Enquiry. For, unlike Malebranche and Berkeley, Hume rejects reason as the basis for our fundamental ontology; its positive function is to correct the ontology rooted in our natural suppositions. 416 Hume's Academic Scepticism fallacious and deceitful' (Enquiry, 159). Indeed, he claims to show that our most natural suppositions about external existence and causality are false.25 Moreover, Hume himself does not purport to be able to live in accordance with the appearances even when it is acknowledged that such a life includes some belief. For while he recommends backgammon and social life in order to dispel the gloomy clouds of Pyrrhonism, he reports that his own natural inclination to philosophy returns shortly after he indulges in these pursuits (Treatise, 269). Philosophy is described as an activity which assigns 'causes and principles to the phaenomena, which appear in the visible world/ In the conclusion to Book I of the Treatise Hume even suggests that the fact that men's minds are inclined toward superstition leads him to enquiries 'without the sphere of common life' (Treatise, 271; but see note 33 below). At the end of his discussion Hume affirms his goal of establishing 'a system or set of opinions, which if not true (for that, perhaps, is too much to be hop'd for) might at least be satisfactory to the human mind, and might stand the test of the most critical examination (Treatise, 272; italics are mine). It is remarkable that the view has prevailed that Hume is a Pyrrhonian sceptic especially in his Treatise of Human Nature. Hume's central aim in that work is to construct a science of man based on experimental method. At the beginning he rejects the claims of those who put forward their hypotheses as 'certain principles' (Treatise, xviii). His own central principles such as the empiricist principle and the principle of association of ideas are put forward at the outset of Book 1 in a quite tentative way. It is quite significant that, immediately after introducing the former principle, Hume allows an exception to it (Treatise, 5-7; cf. Enquiry, 20-1). On the other hand, Sextus Empiricus notes that 'the Pyrrhonian philosopher' makes it a rule to assent 'to nothing that is non-evident.' He does not dogmatize, where dogmatizing means assenting to things which are not absolutely certain (Sextus Empiricus, 11). This is clearly the methodological rule adopted by Descartes in his first Meditation not that adopted by Hume either in his Treatise or his Enquiry Concerning Human Understanding. Both in the Introduction to the Treatise and in the conclusion to Book 1 Hume indicates his willingness to accept principles which are not absolutely certain. 25 Treatise, 213 (lines 15-17), 223 (lines 22-5) 417 John P. Wright II Hume's mitigated scepticism or Academical Philosophy The scepticism which Hume himself adopted is clearly identified in the last section of his Enquiry Concerning Human Understanding as a 'mitigated scepticism or academical philosophy' (Enquiry, 161). While there has always been much dispute about the nature of the original academic scepticism26 there are statements in both Cicero and Sextus Empiricus which clearly distinguish it from Pyrrhonian scepticism. Cicero writes that 'the sole object' of the Academic discussions is 1?y arguing on both sides to draw out and give shape to some result that may be either true or the nearest possible approximation to the truth.'27 The Academics attempt to rid the mind of what they call 'the act of assent, that is of mere opinion and hasty thinking' {Academica, 607). But both Sextus and Cicero stress that while the Academics reject knowledge in the form of the Stoic cataleptic impressions they accept those which are 'probable.'28 Cicero notes that while these probabilities are 'not grasped (non comprehensa ) nor perceived nor assented to/ they 'possess verisimilitude' {Academica, 595). They provide the Academic philosopher 'with a canon of judgement both in the conduct of life and in philosophical investigation and discussion (in agenda vita et in quaerendo ac disserendo)' (Academica, 509). An echo of this latter claim of Cicero appears in Hume's Abstract when he declares that a central aim of his logic is to explain 'probabilities, and those other measures of evidence on which life and action intirely depend , and which are our guides even in most of our philosophical speculations.'29 In the Treatise Hume distinguishes both a wider and narrower sense of the term 'probability' (Treatise, 124); in the Abstract he is clearly using it in the wider Ciceronian sense to label those measures of evidence which do not constitute knowledge. This is the sense in which Locke used the term in the Essay Concerning Human Understanding when he characterized 'Probability' as an agreement or disagreement of 26 See, for example, Gisela Strieker, 'Sceptical Strategies,' Doubt and Dogmatism, 54-83. 27 Cicero, Academica, 475 28 Outlines of Pyrrhonism, 139; Academica, 507-9; see Charlotte Stough, Greek Scepticism (Berkeley: University of California Press 1969), Chapter 3, esp. 40. 29 David Hume, An Abstract ofa... Treatise of Human Nature, in David Hume, A Treatise of Human Nature, 2nd ed., ed. L.A. Selby-Bigge, rev. P.H. Nidditch, 647. 418 Hume's Academic Scepticism ideas whose connection is not 'constant and immutable, or at least is not perceived to be so'; in probabilities, according to Locke, the connection between ideas is sufficient 'to induce the Mind to judge the Proposition to be true, or false, rather than the contrary/30 The central aim of Hume's works on the understanding was to show that we are induced to accept such measures of evidence not because we have an obscure understanding of the connection of the ideas but because of the mechanical, irrational, and unconscious operations of the imagination.31 Hume argues that our supposition of the existence of causal connections between those objects which we call cause and effect is not comprehended, to use the Ciceronian term. At the same time he argues that it is firmly rooted in the principles of imagination and obtains thereby some epistemic validity. Hume accepted the Ciceronian claim endorsed and interpreted by Locke and the Royal Society32 which gives credibility to what is probable. The academic sceptic, unlike the Pyrrhonian, argues both sides of the question in order to obtain some positive result. In Hume's version of this philosophy, this requires that the claims of both the phenomena and the noumena need to be modified. In his Enquiry Concerning Human Understanding Hume says that in the academic philosophy the 'undistinguished doubts' of the Pyrrhonian 'are, in some measure, corrected by common sense and reflection' (Enquiry, 161). This clearly indicates that the realm of doubt is to be limited by giving credibility to the noumena. But these common-sense reflections must in turn be corrected by the reflections on the nature of our ideas which originally led to the 30 John Locke, An Essay Concerning Human Understanding, ed. P.H. Nidditch (Oxford: Clarendon Press 1979), Book 4, Chapter 15, Section 1; Hume adopts Locke's distinction between constant and inconstant connections in Book I, Part III, Sect. I of the Treatise. 31 For a discussion of the relation of Hume's and Locke's views on of probability see John P. Wright, 'Association, Madness, and the Measures of Probability,' in Christopher Fox, ed., Psychology and Literature in the Eighteenth Century (New York: A.M.S. Press, forthcoming). 32 See Barbara J. Shapiro, Probability and Certainty in Seventeenth-Century England (Princeton: Princeton University Press 1983), Chapter 2; also Douglas L. Patey, Probability and Literary Form (Cambridge: Cambridge University Press 1984), Part I, esp. 13-34. On the use of Cicero in the development of earlier modern ideas of probability see Lisa Jardine, 'Lorenzo Valla: Academic Skepticism and the New Humanist Dialectic,' in M. Burnyeat, ed., The Skeptical Tradition, 253-86. 419 John P. Wright unlimited doubts of the Pyrrhonian. Hume writes that 'philosophical decisions are nothing but the reflections of common life, methodized and corrected' (Enquiry, 162). In order to understand the nature of Hume's academic scepticism we need to understand just how the phenomena and the noumena modify each other. As I have indicated, Hume thinks that if we could allow our sensederived ideas to have unlimited sway over our beliefs we would be led to an absolute scepticism. We would be led, as were Malebranche and Berkeley (respectively), to deny finite causal connections and the existence of anything independent of our perceptions. But Hume thinks that we can limit the doubts engendered by these new proponents of divinity or school metaphysics by acknowledging the 'narrow capacity of human understanding' (Enquiry, 162). This means, in part, that we must limit the subject matter on which we are to pass judgment though Hume's view on this varies in different writings.33 But it also means, more significantly, that we must reject all ontological claims based purely on the evidence of our sense-derived ideas. Thus, according to Hume, the claims of our sense-derived ideas cannot be accepted without qualification except in the realm of 'quantity or number' (Enquiry, 165). Instead of concluding that there is no connection between cause and effect , Hume says that we need to recognize that we have 'no adequate idea of power or efficacy in any object' (Treatise, 160). Elsewhere in the Treatise Hume speaks of a 'deficiency in our ideas' (267); and in the Enquiry Concerning Human Understanding he says that we need to recognize that our ideas of cause and effect are 'imperfect' (76). Thus, the realm of doubt is limited in Hume's academic philosophy by maintaining that our ideas do not give us just representations of reality. In rejecting the reality-claims of our ideas besides those of quantity and number Hume was rejecting knowledge. For Hume, like his predecessors, held that knowledge must depend 'solely upon ideas' (Treatise, 70). He makes the adequacy of our ideas a condition for knowledge (Treatise, 29). Since Humean ideas (apart from those of 33 The second form of mitigated scepticism identified in the Enquiry is one in which the mitigated sceptic 'confines' his judgment to 'common life' (162). This scepticism is in fact more extreme than that of the Treatise where, as we have seen (417 above) Hume is willing to go beyond common life in order to combat superstition. In The Sceptical Realism of David Hume (174-5) I have argued that Hume returns to the less extreme form of scepticism in his Dialogues Concerning Natural Religion; it is only because he does so that he is able to carry off his radical critique of natural theology in that work. 420 Hume's Academic Scepticism reflection) are derived from the senses it follows that in denying their adequacy Hume was denying that the evidence of our senses provides a basis for our accounts of what is really the case. Hume was rejecting the ontological claims of the modern day equivalents of the Stoic cataleptic impressions clear and distinct ideas. The ontological claims of Hume's academic philosophy arise from an entirely different source namely the inconceivable suppositions which are rooted in the imagination. Hume maintained that 'the imagination' is 'the ultimate judge of all systems of philosophy' (Treatise, 225); it is this faculty which plays the fundamental role in the project announced in the Introduction to the Treatise of Human Nature that of founding the other sciences on that of human nature. It should be understood that this project forms an essential part of Hume's academic scepticism, for it is an attempt to show that probable suppositions not clear and distinct ideas form the basis for the claims of experimental philosophy. At the same time, the probable suppositions which the academic sceptic accepts are not merely the unexamined claims of the imagination. As Sextus Empiricus noted, the academics made a distinction between different probabilities : 'some they regard as just simply probable, others as probable and tested, others as probable, tested' and 'thoroughly inspected.'34 It is claims of this latter sort which form the basis of those positive views which we find in Hume's own philosophy. Ill Hume's account of external existence It will be thought by many that the interpretation of Hume's philosophy which I am outlining here is incompatible with his account of external existence . While I believe that Hume's realist epistemology is best exemplified in his account of causality I hold that its essentials are also present though in a less clear way in his account of external existence. Thus, before turning to Hume's account of causality I shall show how Hume's theory of inconceivable suppositions applies to what he says about external existence. It is important to distinguish three quite distinct views of external existence which find their way into Hume's analysis. 1. In the first place 34 Sextus Empiricus, 139-41; in using this last phrase I am employing the translation suggested at the bottom of page 140. 421 John P. Wright there is the view of all of us who in our unreflective moments suppose that our sensible perceptions continue to exist while unperceived and are therefore themselves external objects. 2. In the second place there is the 'double existence' theory which 'generally speaking' is supposed by philosophers. According to this theory, sensible impressions represent external objects which are not themselves directly perceived. On this view it is these external objects which are supposed to exist while unperceived. But they are not supposed to be 'specifically different' from perceptions. They are, according to Hume, only thought to have 'different relations, connexions, and durations' (Treatise, 68). 3. Finally there is the 'double existence' theory which is based on the 'fundamental principle of modern philosophy' that 'colours, sounds, tastes, smells, heat and cold' are 'nothing but impressions in the mind, deriv'd from the operation of external objects, and without any resemblance to the qualities of the objects' (Treatise, 226). I believe that it is this theory which Hume has in mind when he talks about supposing a specific difference between perceptions and objects (Treatise, 68). The first two theories are discussed in the chapter of the Treatise entitled 'Of scepticism with regard to the senses'; Hume begins the chapter by saying that this notion of external existence 'when taken for something specifically different from our perceptions' is absurd (Treatise, 188). Nevertheless, he does go on to discuss this theory (our third one) in the chapter entitled 'Of the modern philosophy.' There is a similar division between Hume's discussions of the first two theories and the third at the end of part 1 of Section XII of the Enquiry Concerning Human Understanding. Let me begin my discussion by considering this third theory of external existence. It is wrong to say that Hume dismisses this theory, as is so commonly thought. It is true that, on Hume's view, this theory 'has little or no influence on practice'; at the same time he says that it is 'to be regarded as a considerable advancement of the speculative sciences' (Treatise, 469). Moreover, it is clear that Hume holds that the theory has a solid basis in our experimental reasoning. After describing the relevant observations Hume writes that the conclusion that colours, sounds, etc. are 'nothing but internal existences' which 'arise from causes, which no ways resemble them' is 'as satisfactory as can possibly be imagin'd' (Treatise, 227). Finally it is clear in some sense that we all are able to suppose what it would be like for this theory to be true: there would have to be independently existing primary qualities extension, solidity, and motion without any secondary ones. However, Hume follows Berkeley in arguing that we cannot form any idea of such an object; for it is, say these writers, impossible to con

Hume's Academic Scepticism ceive primary qualities without secondary ones. The problem is that the primary qualities are only conceived by abstraction and hence cannot, according to what Hume calls the 'establish'd maxim in metaphysics' (Treatise, 32), represent things or substances. Thus we are left with the notion of something which is related to our perceptions as the cause of them but of which we cannot form any idea: The farthest we can go towards a conception of external objects, when suppos'd specifically different from our perceptions, is to form a relative idea of them, without pretending to comprehend the related objects' (Treatise, 68). Thus at the end of the section 'Of the modern philosophy' we appear to be left in the utmost scepticism regarding the external object (Treatise, 231). It is impossible to conceive of such a thing. For Berkeley, that is the end of the matter. However, I think there is good reason to think that this is not true for Hume. After presenting this argument in his Enquiry Hume notes that it is 'drawn from Dr. Berkeley' and claims that it is 'merely sceptical' in that it admits of 'no answer and produce [s] no conviction (Enquiry, 155). That doesn't tell us whether the fundamental principle of modern philosophy is true or false. But the direct parallel which Hume draws between this principle and his own principle that moral virtue and vice are not qualities in objects (Treatise, 469) suggests that the former theory as well as the latter has a clear significance in his own philosophy. Moreover, as we have seen, Hume states that we 'may suppose ... a specific difference betwixt an object and impression' even where we cannot conceive one (Treatise, 241). Thus, it seems that we may suppose matter to exist solely with primary qualities even though we cannot conceive it to exist in this way. And we have good reason to make this supposition given that, according to Hume, the theory is based on a systematic application of the principle of cause and effect (cf. Treatise, 231 last paragraph). Hume's remarks on this theory are too paradoxical to allow us to come to any definitive interpretation of his own views. It is clear however that the most fundamental theory of external existence that which we all hold prior to any philosophical reflection also depends on a supposition that external objects have different properties than our sensible perceptions or impressions. This may seem to be a puzzling claim since that theory makes no distinction between the impressions and external objects: as I mentioned earlier Hume thinks that in the uncritical state of mind in which we accept that theory we 'suppose, that the very being, which is intimately present to the mind, is the real body or material existence' (Treatise, 206). But Hume also holds that we are supposing what is not really the case. Direct realism is false. For, as a matter 423 John P. Wright of fact, the immediate objects of our sense perception cease to exist as soon as they are not perceived.35 However, Hume sometimes characterizes this common-sense assumption in more neutral terms: we provide a continuity for our experience 'by supposing that ... interrupted perceptions are connected by a real existence, of which we are insensible' (Treatise, 199). In this general form the supposition is not false for the real existence which connects our perceptions need not be the continuing existence of the perception itself.36 And, of course, what we are really doing (though we are not reflectively aware of it) is ascribing a property (continuing existence) to the object, which our impressions do not possess. The fact that Hume stresses that the principles by which we ascribe an unperceived existence are 'conducted by such false suppositions ' (Treatise, 217) should not blind us to the fact that they also lead us to make a true one. Toward the end of Book I of his Treatise Hume speaks of an 'irregular kind of reasoning from experience' which makes us 'discover a connexion or repugnance betwixt objects, which extends not to impressions.' He cites as an example his earlier account of the ascription of unperceived existence on the basis of the 'coherence of our perceptions ' (Treatise, 242). In that account he had noted that 'we suppose' that 'objects still continue their usual connexion' even when they are unperceived and that 'irregular appearances' (such as the sound of a creaking door without the visual impression of the door) 'are join'd by something, of which we are insensible.' In forming this 'simple supposition of their contin'd existence' (Treatise, 198) we still make a mistake in so far as 'we confound perceptions and objects, and attribute a continu'd existence to the very things [we] feel or see' (Treatise, 193). However, there is still something correct about our natural supposition of continued existence.37 35 Treatise, 210 (lines 10-15); Treatise, 217 (lines 30-5); Enquiry, 152 (lines 28-32) 36 Compare my The Sceptical Realism of David Hume, 55-6. I have given an extended analysis of Hume's account of our belief in external existence in Chapter 2. For reasons which emerge in the present paper I am now less inclined to call Hume's theory of perception a representative one than I was when I wrote this chapter. Hume certainly holds an indirect theory of perception: but it is important to note that, according to him, one cannot simply read off the features of reality from our ideas and impressions. 37 The centrality of 'suppositions' in Hume's account of external existence was suggested to me in reading through Chapter IX of John Yolton's Perception Acquaintance from Descartes to Reid (see especially the section entitled 'Suppositions and False Beliefs' [173-6]). But I think that suppositions play a wider role in Hume's 424 Hume's Academic Scepticism This is apparent from Hume's treatment of the theory to which philosophers generally subscribe. According to this theory, perceptions represent external objects which cause and resemble them. Hume claims that this theory arises from the rational criticism of the common sense theory when we discover that our immediate sense perceptions are mind-dependent existences. Thus philosophers including Hume38 distinguish 'betwixt perceptions and objects, of which the former are suppos 'd to be interrupted, and perishing, and different at every return; the latter to be uninterrupted, and to preserve a continued existence and identity ' (Treatise, 211). But Hume stresses that his belief in a double existence of perceptions and objects has no independent evidence to support it and that it is itself dependent on the natural supposition which led to the view of common sense. That is to say that the philosopher has no basis for a supposition that anything exists while unperceived except the principle of the imagination which originally led us to suppose the continuing existence of our perceptions themselves. Moreover, philosophers generally rely on other principles of imagination which make us 'suppose our objects ... to resemble our perceptions' and that the former cause the latter (Treatise, 217). Hume holds that the true philosopher needs to correct at least the first of these two natural suppositions but insofar as he himself accepts any of the features of this representative system he is still dependent on the suppositions of common sense. Even though this system cannot claim the direct evidence of our impressions and ideas it is based on a rational correction of the natural propensities of the imagination . Each of the theories of external existence which Hume considers involves a supposition that objects are, in some sense, different from their corresponding impressions. As I pointed out at the beginning of this discussion, I do not think that Hume's own realist epistemology emerges ontology than Yolton may originally have realized and that it is important to recognize that, according to Hume, suppositions of the imagination rather than genuine sense-derived ideas provide the basis for our ontology. 38 Treatise, 67 (lines 20-4), 239 (line 23-6); Enquiry, 152 (lines 18-22). On page 202 of the Selby-Bigge edition of the Treatise Hume tells his reader that he will temporarily withhold this distinction in order to accomodate himself to the thinking of the vulgar; the distinction is reintroduced on page 211. Compare John Passmore, Hume's Intentions, revised edition (London: Duckworth 1968), 90-1; Anthony Flew, Hume's Philosophy of Belief, (London: Routledge and Kegan Paul 1961), 47; N. Kemp Smith, The Naturalism of David Hume,' Mind 14 (1905) 149-73, 335-47, esp. 169-70. 425 John P. Wright perfectly clearly from his accounts of our supposition of external existence . However, it should be noted that in each of these accounts he stresses that our belief in external existence involves suppositions which cannot be based on the evidence of our senses and reason. Indeed, according to Hume, an examination of our sense-derived ideas reveals that external existence cannot be clearly and distinctly conceived. Nevertheless , Hume himself observes a distinction between objects and perceptions throughout his writings on human understanding and such a distinction, insofar as it is presupposed by his own claims about the deficiency of our ideas, lies at the root of his academic scepticism. IV The Supposition of Necessary Causal Power The complexities and paradoxes contained in Hume's account of external existence leave one with no very clear picture of the role which these suppositions play in his own epistemology. The clearest development of the theory is in his account of our causal inferences. Hume's scientific methodology has commonly been interpreted as a kind of 'observationalism' which denies that 'unobservables' have any place in scientific enquiry. In an interesting recent article, J.P. Monteiro has argued persuasively that unobservable 'powers and qualities' play an important role in Hume's own science of human nature. But Monteiro still endorses the view that Hume's theory of 'causal inference' involves no more than an inference from past observations to future ones.39 This does not seem to me to be correct. It is the very essence of our causal inferences and judgments, as analyzed by Hume both in the Treatise and the Enquiry, that they take us beyond our perceptions and make us suppose that there are caus&l powers in objects. In section I of this paper I pointed out a passage from the Enquiry in which Hume claims that in ordinary life we suppose that we actually perceive the force or energy by which the cause is connected with its effect . Later on in the same section he identifies this as the supposition that there is a necessary connection between the cause and the effect: '... When one particular species of event has always, in all instances, been conjoined with another, we ... call the one object, Cause; the other, £/39 J.P. Monteiro, 'Hume's Conception of Science/ Journal of the History of Philosophy 19 (1981), 327-42 426 Hume's Academic Scepticism feet. We suppose that there is some connexion between them; some power in the one, by which it infallibly produces the other, and operates with the greatest certainty and strongest necessity' (Enquiry, 74-5). This natural supposition is based on a feeling we have when we have experience two events as constantly conjoined. As a result of an association of ideas one 'feels these events to be connected in his imagination' (Enquiry , 75-6). This feeling of inseparability of the two events is not the recognition of a logical connection between them but it makes us form a judgment which is equivalent to one which we would have if we actually apprehended such a logical inseparability. In his Treatise Hume writes: Tis natural for men ... to imagine they perceive a connexion betwixt such objects as they have constantly found united together; and because custom has render'd it difficult to separate the ideas, they are apt to fancy such a separation to be in itself impossible and absurd' (Treatise, 223). Indeed, as Kant pointed out in his Prolegomena, Hume thinks that we mistake 'a subjective necessity' arising from custom and habit for 'an objective necessity arising from insight.'40 But, however confused the judgment, the result is the same. We naturally suppose that there is an objective necessity linking those events which we have constantly experienced in succession.41 How then does the academic philosopher's view of causality differ from that of common sense? As we have seen, in both the Enquiry and Treatise, Hume stresses that the common man supposes that he actually perceives the power or necessary connection which links the effect to the cause. But the academic philosopher, who has analyzed his impressions and ideas, knows that this is false. He knows that the connection which the common man ascribes to the objects is not perceived. Hume writes that '... Philosophers, who abstract from the effects of custom, and compare the ideas of objects, immediately perceive the falshood of these vulgar sentiments, and discover that there is no known connexion among objects' (Treatise, 223; italics are mine). Still, the academic philosopher (who seeks to found the sciences on the principles of the imagination 40 Immanuel Kant, Prolegomena to any Future Metaphysics, translation revised by L.W. Beck (Indianapolis: Bobbs-Merrill 1950), 6 41 In this paragraph I have outlined one of Hume's accounts of our belief in objective necessity. This coincides with one of two accounts which Hume presents in his Treatise. For a more complete description of Hume's theories and an account of the historical roots of the theory presented here see Wright, The Sceptical Realism of David Hume, 151-4. 427 John P. Wright 'which are permanent, irresistable, and universal'42) gives credence to the basic natural principle on which the common man's belief is based. He recognizes that without the natural supposition we will be driven to the absurd view that there are no causes in the universe. Thus the proponent of what Hume calls the 'true philosophy' returns to 'the sentiments of the vulgar' insofar as he ascribes a causal power to the object whenever he discovers a regular succession. However, he recognizes that he has no actual perception of the power by which the events are necessarily connected (Treatise, 222-3). It is easy to read into some of Hume's remarks the view that there is no genuine connection in objects. But I believe that this is a mistake. In the passage I have just discussed Hume also contrasts the view of the true philosophy with that of a 'mistaken knowledge' and he says that the proponents of the latter continue to seek for 'a natural and perceivable connexion ... in matter, or causes.' He says that they 'seek for it in a place, where 'tis impossible it can ever exist.'43 Is Hume not saying that necessary connection and power cannot exist in objects? In fact, the error he is ascribing to the false philosophers is based on the fact that they continue to seek for a perceivable connection in objects. What cannot exist in objects is anything corresponding to the actual idea we have. What the proponent of the false philosophy fails to recognize is that 'we have no idea of power, or agency, separate from the mind and belonging to causes' (Treatise, 223; my italics). For the actual idea we have is merely based in a subjective feeling of constraint which arises from the mind's own mechanisms. But this does not mean that there can be no power or necessary connection in objects. Hume himself says that he is quite willing to allow that 'there may be several qualities both in material and immaterial objects, with which we are utterly unacquainted.' (He even talks of 'meaning these unknown qualities.'44) Indeed this is an acknowledge42 There is really a two stage process by which the academic philosopher's view is obtained. In the first place Hume claims that his view, unlike the view of ancient philosophers, is based on principles of imagination which have the natural characteristics cited here. But this is also true of vulgar belief. In order to reach what is distinctive in the academic philosopher's view a further refinement is necessary namely an examination of the nature of our ideas through reason. 43 Treatise, 223; it is important to note that the grammatical reference of the pronoun 'it' in the second last line on this page is 'a natural and perceivable connexion .' Similarly at Treatise, 168 that which Hume says 'is incompatible with those objects, to which we apply it' is 'something, of which we have a clear idea.' 44 Treatise, 168; my italics. In this passage Hume is clearly using the term 'meaning' 428 Hume's Academic Scepticism ment which must be made by the true philosopher who seeks to base his fundamental ontology on the same principles of the imagination which originally led to the view of the vulgar not on representative ideas.45 The importance of the academic philosopher's commitment to the existence of an unperceived necessary connection is clear in a brief account of scientific method which Hume presents both in his Treatise and in his Enquiry. According to this account, scientific investigation has its beginnings in those cases where a previously observed regularity fails to hold. In this case there is a distinction between the opinion of the common man and that of the philosopher: whereas the former attributes the exception to an 'uncertainty in the causes' that is, to chance the philosopher assumes that it arises from the 'secret operation of contrary causes.' For the fact that he frequently discovers causes which 'are hid, by reason of their minuteness or remoteness' leads the philosopher to 'form a maxim, that the connexion betwixt all causes and effects is equally necessary' (Treatise, 132; cf. Enquiry, 86-7). Thus the philosopher or scientist, unlike the common man, ascribes an unperceived necessary connection even in those cases where he fails to observe a constant conjunction between events. Elsewhere Hume writes that 'Even when ... contrary experiments are entirely equal, we remove not the notion of causes and necessity; but supposing that the usual contrariety proceeds from the operation of contrary and conceal'd causes, we conclude, that the chance or indifference lies only in our judgment on account of our imperfect knowledge, not in the things themselves, which are in every case equally necessary, tho to appearance not equally constant or certain {Treatise 403-4; my italics). In the Treatise Hume tried to argue that this scientific belief in universal necessity is indirectly rooted in natural principles of differently than he does in the statements of his empiricist principle (see especially Enquiry, 22). He seems to have an alternative 'intentional' conception of meaning. Michael Williams remarks that we need to consider 'that "meaning" is by now a technical notion in a way that it never was for Hume. Accordingly ... although Hume regards various terms as "insignificant," it is far from clear that such terms are thought of as entirely devoid of "meaning" ' (Williams, 'Hume's Criterion of Meaning,' 276). The interesting thing about the passage under discussion is that Hume regards words like 'power' as having a meaning, even though they are meaningless according to the empiricist principle. 45 Compare here Berent Enc, 'Hume on Causal Necessity: A Study from the Perspective of Hume's Theory of the Passions,' History of Philosophy Quarterly 2 (1985), 235-56, who discusses the non-representative character of the idea of causality in Hume's account. 429 John P. Wright the human mind. Nevertheless, it is clear that he assumes that scientific reasoning, unlike the reasoning of everyday life, is guided by a belief in an unperceived universal necessity. Hume's account of scientific discovery which is based throughout on a belief in a hidden causal necessity is a plausible one. For example, according to this account an unscientific person would say that it is just a matter of chance that the tail section of a certain aeroplane has broken off during flight. But the scientifically minded person that is, the experimental natural philosopher will continue to assume that the stress tests that have been done indicate some necessary connection between the fact that steel has been prepared in a certain way and the fact that it will withstand certain amounts of pressure. He will not merely say that his earlier judgment was fallible; he will insist that there really is some power or force in the steel which allows it to stand up under so much pressure. Thus he will look for a hidden causal factor which is operating in the case where the steel has buckled. Is there some difference in the steel that was used in the tests than that which was used in the actual aeroplane? Were there unusual pressure conditions which would account for the fact that the steel has buckled in the exceptional case? And so on. Because he assumes that there are unperceived necessary connections between the cause and the effect, even where there is an exception to a general regularity, the philosopher will look for some hidden difference in the cause in the exceptional case. Thus he might discover a certain change in the structural properties of steel after ten continuous years of use that will cause it to lose its original rigidity. On Hume's view the discovery of such a hidden cause results from the supposition that there is an absolute necessity in nature, even where an established regularity fails to hold. Of course, Hume's academic scepticism does not stop here. It is not merely that we have not yet discovered the actual power by which causes produce their effects; Hume holds that we probably never will discover this power. In his Enquiry Hume wrote that the 'ultimate springs and principles are totally shut up from human curiosity and enquiry. Elasticity , gravity, cohesion of parts, communication of motion by impulse; these are probably the ultimate causes and principles which we shall ever discover in nature' (Enquiry, 30). At bottom, Hume's causal scepticism does not rest on what is sometimes called his fallibalism I seriously doubt that Hume suspected that exceptions would ever be found to the laws discovered by Newton but rather in his belief that the real power and force of nature cannot be comprehended by human beings. Yet Hume also stresses that the absence of awareness of the real power 430 Hume's Academic Scepticism should not hinder us in our ascription of that power. In his Treatise he wrote that 'the cohesion of the parts of matter arises from natural and necessary principles, whatever difficulty we may find in explaining them' (Treatise, 401). And, more generally, in his Enquiry he writes that 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' (Enquiry, 82). This is a belief which is not in any way threatened by Hume's academic scepticism . His aim in the chapters from which I have just quoted is merely to insist that the regularity we discover in human affairs is sufficient to indicate a similar necessity in human behaviour. It is tempting to say that the supposition of power and efficacy can easily be eliminated from Hume's philosophy, even though he himself never did eliminate it. At the very least, it will be said, there is no loss in regarding as 'Humean' a philosopher who is agnostic about the existence of such a power. It will be said that, since Hume himself admits that one is aware of nothing more than constant conjunction, the belief in the hidden causal necessity falls out as irrelevant. The problem with such a point of view is, I believe, that it leads us away from what is really central in the philosophy of Hume himself. In the first place, it is based on a fundamental misunderstanding of Hume's own attitude toward 'scepticism.' In the second, it leads to a misunderstanding of Hume's conception of scientific method. In the third place, it fails to take into account Hume's role in those eighteenthcentury theological debates which were so central to his own philosophy. Let me briefly consider each of these points. I have already noted Hume's own stress on the fact that 'agnosticism' on basic metaphysical propositions is not possible: on questions of fundamental ontology, mitigated scepticism is not a matter of 'suspension of belief.' No matter how refined our reflection, we are in fact dependent on natural suppositions imposed on us by our imagination. That is a central point of Hume's philosophy of the understanding. According to Hume, the judgment of objective necessary connection forms a fundamental and ineliminable part of our natural supposition of causality. Secondly, Hume's own theory and practice of science reveal his belief that discovery involves a good deal more than an attempt to uncover general correlations. In the passage on scientific method which I have discussed, Hume conceives of the search for hidden causes as the search for mechanical ones. Mechanical models played a key role in Hume's identification of the principles of the imagination in the Treatise. 431 John P. Wright Moreover, unlike his contemporaries such as Berkeley and Reid, Hume stressed and approved of the role of hypotheses in science. This is nowhere more evident than in his approval of Newton's aether hypothesis, which he initially took to involve the postulate of an active matter.46 I think that it is clear that Hume thought that modern science had revealed the natural and necessary principles of nature to some extent . Finally, the view that causality amounts to no more than lawlike regularity obscures the whole role that his theory of causality played in eighteenth-century theological debate. The standard view accepted by Clarke, Locke and Newton was that there is an obvious necessity in mechanical causation: a mechanical cause necessarily brings about its effects . Clarke and Newton (as well as contemporary opponents of Hume such as John Stewart) held that regularities which were not reducible to mechanism such as that of gravitation revealed more or less directly the efficacy of a free agent. Now Hume himself argued that since we perceive no more than constant conjunction in both cases, we have as much reason to suppose a necessary causal power in the second case as the first. In other words, there is no reason to postulate a non-necessary voluntary agent in the case of causes which cannot be reduced to mechanical ones. Now, this argument would I think lose its point unless it were assumed that constant conjunction and law-like succession reveal a genuine necessity in nature.47 In reflecting on the role of the natural supposition of necessary connection in the academic sceptic's interpretation of the world it is useful to reflect on the origins of the account of epistemic justification which is implicit in Hume's account. I believe that this account has it origins in the discussion of the external world in Nicolas Malebranche's The Search After Truth. In that work Malebranche had argued against Descartes' view that the existence of the external world can be proved that is, be known to us through reason alone. However, Malebranche went on to claim that we have a very strong inclination to judge that our sensations are caused by objects independent of us and that the very existence of such an inclination provides some justification for the natural judgment that we form. Moreover, Malebranche held that there is an aspect of the natural judgment which is false namely, the belief that the sensible 46 For an elaboration of these points see my The Sceptical Realism of David Hume 15-16, 204-21, 145-7, 162-3. 47 See Wright, The Sceptical Realism of David Hume, 163ff . 432 Hume's Academic Scepticism qualities like colour, sound, etc. are really in the external objects. According to him, this aspect of our natural judgment can be proved false by reason. According to Malebranche's theory we have good reason to consider as true that which we are strongly inclined to judge as such unless our judgment can be shown to be false. We cannot show that there are no independent objects which cause our sensations so that aspect of our natural judgment holds up. Thus Malebranche says that his argument should establish that the existence of things outside of us is 'entirely probable/48 I believe that it was essentially this epistemic theory which Hume successfully applied in his account of our causal suppositions. There is a clear precedent for the link between natural supposition and 'probability' in the writings of Malebranche. One might say that Malebranche's theory of natural judgment is an ancestor of Hume's theory of natural supposition.49 On Hume's theory one cannot say that our natural suppositions are absolutely true. Yet those suppositions which are based on the permanent, irresistable and universal principles of the imagination have prima facie credibility. We need to scrutinize them according to reason and, in so doing, rid them of those aspects which can be shown to be false. What we are left with is an interpretation of reality which has a high degree of probability that is, a likeliness to be true.'50 Thus men naturally suppose that objects which are constantly conjoined are necessarily connected and that such a connection is immediately perceived . Reason shows the falsity of the second part of this natural supposition . However, the first part loses none of its credibility and, according to Hume, provides the probabilistic basis of modern science. Conclusion I have been arguing that a 'realism' is built into Hume's account of both the ordinary man's and the scientist's judgments of external ex48 Nicolas Malebranche, The Search After Truth, trans. Thomas M. Lennon and Paul L. Olscamp (Columbus: Ohio State University Press 1980), 572-4 49 On the connections between Malebranche's and Hume's theories see Wright, The Sceptical Realism of David Hume 64-71, 74-6, 85-6, 224ff., and C.W. Doxsee, 'Hume's Relation to Malebranche,' Philosophical Review 25 (1916), 692-710. 50 This is Locke's reading of the term 'probability' in Book 4, Chapter 15, Section 3 of his Essay Concerning Human Understanding. 433 John P. Wright istence and causality. I have also suggested that scientific judgments those adopted by the mitigated or academic sceptic embody a theory about the limits of human understanding and the way those limits are overcome by human nature. The mitigated sceptic of the Enquiry even adopts a theory of 'preestablished harmony between the course of nature and the succession of our ideas' which explains how through our instinctual suppositions we gain some sort of purchase on reality. According to this theory, nature 'has implanted in us an instinct, which carries forward the thought in a correspondent course to that which she has established among external objects; though we are ignorant of those powers and forces, on which this regular course and succession of objects totally depends' (Enquiry, 54-5). Further, as Monteiro has shown, in the Dialogues Concerning Natural Religion, Hume's Philo suggests a primitive Epicurean evolutionary theory to explain the existence of such adaptive mechanisms.51 While the elements of the theory are clearly not totally based on reason in Hume's sense of the term they do give the academic sceptic more than practice to fall back on in accounting for the principles which he adopts. It seems likely that it was at least the initial part of this theory which Hume had in mind when he advocated his own 'system or set of opinions' at the end of Book 1 of his Treatise of Human Nature. Since the view that there are unknown objects and powers would appear to be incompatible with the generally accepted view of Hume as an 'empiricist,' it is worth considering the question whether Hume really embraces the view usually called empiricism. One can say straightforwardly that Hume is not an empiricist if that word is used to connote a philosopher who identifies reality with his sense-impressions. But if by an empiricist we mean a philosopher who argues that our judgments about what exists are founded on experience and observation52 rather than our sense-derived ideas, then Hume certainly is an empiricist. But, what Price called the 'permanent significance' of Hume's philosophy of the understanding lies in his analysis of experience itself. Hume attempts to show that both our common sense and scientific experience of reality 51 J.P. Monteiro, 'Hume, Induction, and Natural Selection,' in David Norton, Nicholas Capaldi, Wade Robison, eds., McGill Hume Studies (San Diego: Austin Hill Press 1979), 291-308 52 On page 191 of his Treatise, Hume makes a clear contrast between what we can say about our sense impressions and what we determine on the basis of 'experience and observation.' 434 Hume's Academic Scepticism take us beyond the data of sense and that the process by which we draw experiential conclusions has its grounding both de facto and de jure in the instinctual suppositions of the organism itself. I began my discussion by noting Hume's claims in The Sceptic' and the Enquiry Concerning the Principles of Morals that the standards of truth in scientific investigation are independent of human beings and are often unknown. Hume's writings on human understanding especially on causality suggest that the object, in its very essence, lies outside of human comprehension. In experience we gain information about the world without any genuine understanding of the object we experience. Let me close my remarks by contrasting briefly Hume's realist analysis of experience with that of the philosopher who undoubtably gave the best expression of the phenomenalist account of our apprehension of reality namely, Hegel. According to Hegel, 'experience' must be understood as a dialectical movement which affects both knowledge and its object. Hegel regarded experience as a process whereby an object previously considered outside of knowledge comes to be known. The previously unknown object 'in being known, is altered for consciousness; it ceases to be the in-itself , and becomes something that is the in-itself only for consciousness. And this then is the True: the being-forconsciousness of this in-itself ... This new object ... is what experience has made of it.'53 For Hegel, truth is nothing more than the current absorption of the object into human consciousness by way of the process of experience. The object is in a constant process of being swallowed up by the subject. In contrast, Hume regarded truth as invariable by human apprehension . And he attempted to give an analysis of experience in which the object itself is never directly apprehended. This analysis lies at the heart of the academic scepticism adopted by Hume in his discussions of human understanding.* Received February, 1985 53 G.W.F. Hegel, Phenomenology of Spirit, trans. A.V. Miller (Oxford: Oxford University Press 1977), 55 * Earlier versions of this paper were read to symposia of the Canadian Philosophical Association and the Hume Society at which my book The Sceptical Realism of David Hume was discussed. I am indebted to Bruce Hunter and Terence Penelhum whose comments for the C.P.A. symposium in 1984 stimulated the original draft of the paper and to the readers for the Canadian Journal of Philosophy who made helpful suggestions for revision.