Chapter 8. Chapter 9. Chapter Goals. Suggested Weblinks. Flashcards of Key Terms. Chapter Instructor Resources. Contact Your Sales Rep. Higher Education Comment Card. Chapter Summary. Arc 1 : The conclusion that an all-perfect God exists is derived from premises that are clearly and distinctly perceived — i. Arc 2 : The general veracity of propositions that are clearly and distinctly perceived is derived from the conclusion that an all-perfect God exists.
The italicized segment of Arc 1 marks an addition to the original statement of it, thereby clarifying the circularity reading. Interpreted in this way, Descartes begins his Third Meditation proofs of God by presupposing the general veracity of clear and distinct perception.
If there is one point of general agreement in the secondary literature, it is that the texts do not sustain this interpretation. How then should Arc 1 be understood? There are countless interpretations that avoid vicious circularity, along with numerous schemes for cataloguing them.
Arc 1 : The conclusion that an all-perfect God exists is derived from premises that are clearly and distinctly perceived — indeed, premises belonging to a special class of truths that are fully immune to doubt prior to establishing the general veracity of propositions that are clearly and distinctly perceived. Again, the italicized segment marks an addition to the original statement of Arc 1. More precisely, the Evil Genius Doubt is on this reading bounded in the sense that its sceptical potency does not extend to all judgments: a special class of truths is outside the bounds of doubt.
Exemplary of this special class are the cogito and, importantly, the premises of the Third Meditation proofs of God. Propositions in this special class can be perfectly known, even by atheists. Thus, the need on this interpretation for Arc 2 in the broader project. The other main kind of interpretation avoids circularity in a different manner. More precisely, the Evil Genius Doubt is on this reading unbounded in the sense that it undermines all manner of judgments — even the cogito , even the premises of the Third Meditation proofs of God — when the mind is no longer attending to them clearly and distinctly.
Insofar as the meditator assents to the steps of these proofs, he does so not because of having an understanding of clear and distinct perceptions as being guaranteed true, but because the mind cannot but assent to them while attending clearly and distinctly.
Importantly, if doubt is thus unbounded there is no circularity. The premises contributing to the conclusion of an all-perfect God remain vulnerable to hyperbolic doubt. It is the unboundedness of hyperbolic doubt that underwrites the No Atheistic Perfect Knowledge Thesis.
A central feature of this interpretation is worth repeating. It is natural for critics to ask why the arguments of Arc 1 are accepted by the meditator if, indeed, Evil Genius Doubt remains in play. The answer lies in our earlier discussion of the indirect manner in which the doubt undermines clear and distinct perception Section 4.
However, the meditator does not yet have perfect knowledge of those premises, nor of their conclusions. How, then do those matters finally rise to the status of perfect knowledge? We return to this issue, below. At present, the focus is on the issue of circularity. Though bounded and unbounded doubt interpretations both avoid vicious circularity, each confronts further difficulties, both textual and philosophical. Unbounded doubt interpreters must explain why, in the final analysis , the Evil Genius Doubt eventually loses it undermining potency.
The first proposition is included in the list of examples that are undermined by the Evil Genius Doubt see the fourth paragraph of the Third Meditation. The second proposition is a premise in a Third Meditation argument for God — a proposition immune to doubt, according to bounded doubt interpretations.
What is supposed to be the relevant difference between these propositions? Given the indirect manner in which Evil Genius Doubt operates, there seems no clear explanation of why the doubt succeeds in undermining the first proposition but is somehow resisted by the second.
Further awkward for this interpretation is that the cogito is included in the list of examples that that same fourth paragraph passage implies is vulnerable to doubt. Granting an unbounded doubt interpretation, why — in the final analysis — does the Evil Genius Doubt eventually lose its undermining potency?
But precisely such moments are when hyperbolic doubt does its undermining work. This means that upon diverting attention from the premises of Arcs 1 and 2, it is then possible to run the Evil Genius Doubt on their conclusions. It would thus seem that unbounded doubt interpretations leave us in a Sisyphus-like predicament.
According to the myth, each time Sisyphus pushes his boulder near to the top of the hill, the boulder somehow slips away, rolling to the very bottom, and the whole process must start all over. By carefully constructing the arguments of Arcs 1 and 2, the meditator gains anti-sceptical momentum, pushing his project near to the goal of perfect knowledge.
Again, the hard question for unbounded doubt interpretations: Why, in the final analysis, does the Evil Genius Doubt eventually lose it undermining potency? One recent unbounded doubt interpretation Newman and Nelson offers a solution, including an explanation of why Descartes waits until the end of the Fifth Meditation to claim final victory over the sceptical problem.
Here is a sketch of the account. It thus seems that a final solution to the problem would need, somehow, to make it no longer possible to make sense of the relevant sceptical scenarios.
Indeed, the interpretation has it the sceptical scenarios become self-evidently incoherent. The needed apprehension of God would need to be self-evident. For suppose my apprehension is grounded in a demonstration. Thus, the needed apprehension of God is a self-evident, clear and distinct conception that renders — as literally unthinkable — the very sceptical scenarios that underwrite indirect doubt. A useful analogy lies in the doubt-resisting character of the cogito. If I attempt a direct doubt of own my existence, the effort is self-stultifying; I immediately apprehend that I must exist, in order to attempt the doubt.
What Descartes needs is a similarly strong and immediate doubt-resisting outcome in connection with attempts at an indirect doubt. That is, on occasions of trying to undermine clearly and distinctly perceived matters — e. The Fifth Meditation introduces various themes about innate truths, including the positive epistemic effects of repeated meditation: truths initially noticed only by means of inference might eventually come to be apprehended self-evidently.
In the build-up to the passage claiming that the Evil Genius Doubt is finally and fully overcome, Descartes writes:. Given his newfound epistemic standing, the meditator would be unable to make coherent sense of the Evil Genius Doubt. His clear and distinct perceptions would be fully indubitable, thereby counting as perfect knowledge.
The interpretation helps explain two passages wherein Descartes purports to be detailing the final solution to the sceptical problem. In both passages, he can seem simply to be asserting that sceptical doubts are impossible, as if having forgotten the indirect manner in which his own hyperbolic doubt operates.
But if we take Descartes to be assuming that the apprehension of God has become utterly self-evident, both passages make more sense. The one passage arises in the Second Replies, in the context of rebutting an objection to the effect that, in the final analysis, it remains possible to doubt clear and distinct perception.
The other passage arises in the Fifth Meditation, in the concluding summary explanation of how the sceptical problem is finally overcome. Absent a self-evident apprehension of God, the two passages appear inexplicable, with Descartes seeming to misunderstand the sceptical implications of his own Evil Genius Doubt.
But on the self-evident God interpretation, both passages read as a summary of the anti-sceptical effects of it being impossible to conceive of God as a deceiver. The interpretation also makes sense of why the final victory over scepticism is announced not at the end of the Fourth Meditation, but at the end the Fifth — after the further result concerning an enhanced, self-evident apprehension of God. To help clarify this further circle, Della Rocca focuses on a twofold question:.
As Della Rocca understands the broader Fourth Meditation argument, the claim that we should assent only to what we clearly and distinctly perceive is an essential step in the ongoing argument to establish the divine guarantee of clear and distinct perception. Since this step presupposes the eventual conclusion, that conclusion is based on circular reasoning:.
Perhaps we can avoid this alleged circle. Though Descartes can be read in this way, the texts support the following alternative understanding of the broader argumentative narrative. Early in the Third Meditation, having reflected on the epistemic impressiveness of the cogito , the meditator discovers that all , but only , clear and distinct perceptions are utterly assent-compelling. However, no step of that demonstration presupposes that clear and distinct perceptions have already been established as true; i.
Summarizing the key steps:. Granted, the meditator needs each of the demonstrative steps to be clearly and distinctly perceived. However, he needs this not because of presupposing the conclusion to be proved, but in order to be in compliance with his own initial resolve, stated in the First Meditation.
We noted in Section 1. Consider again the relevant Second Replies passage:. Indeed, the passage is plausibly read even more strongly: i. Why does Descartes not add a truth condition, thereby ensuring that beliefs counting as perfect knowledge are true? In an influential book, Harry Frankfurt offers a provocative answer. Writes Frankfurt:. The suggestion here is of some version of a correspondence theory. Also, on the most straightforward reading of the epistemic moves in the Meditations , Descartes is presupposing that at least some truths involve extramental metaphysical relations.
Consider that Evil Genius Doubt is, fundamentally, a worry not about whether our various clear and distinct judgments cohere , but about whether they accurately represent an extramental reality — i. Interestingly, Frankfurt himself came to renounce the interpretation:.
How then should we interpret the Second Replies passage, and how should we understand the absence of a truth condition? I suggest that the lack of a truth condition need not reflect an indifference about truth, as opposed to a view about how a concern for truth is properly expressed in an account of knowledge.
We can understand Descartes as wanting a fully internalist account whereby all conditions of knowledge are accessible to the would-be knower. On a justified belief rendering, his account of perfect knowledge is fully internalist; yet, with the addition of a truth condition, it is not — at least, not given a correspondence theory of truth, in the context of metaphysical realism.
Importantly, then, in attributing to Descartes a justified belief account, we need not thereby attribute to him an indifference concerning truth. Again, from that same passage:. Hatfield , , who expresses a related objection. Descartes himself makes a related point in connection with an atheist geometer who happens never to doubt his beliefs, simply because the Evil Genius Doubt never occurs to him:.
But note that the objection is telling only insofar as the requisite indubitability is understood as merely psychological. Yet clear texts indicate that Descartes regards clear and distinct perception as having epistemic import beyond mere doubt-resistance.
His use of light metaphors, including the association of clarity and distinctness with the natural light , strongly convey a form of rational insight.
Imagine that the magic pill is so magical as to instill in us a clear and distinct understanding of the matters we perceive — i. But this objection misses a key point. As suggested in the Second Replies passage, Cartesian certainty — understood in terms of indubitability — does not, strictly speaking, rule out the broad possibility that we are in error.
For texts concerning his final solution to hyperbolic doubt: see Fifth Meditation; Second Replies; letter to Regius 24 May For discussions of the role of the Fifth Meditation in the eventual, self-evident apprehension of God, see Newman and Nelson , Nolan , and Nolan and Nelson For examples of bounded doubt interpretations, see Broughton , Doney , Della Rocca , Kenny , Morris , Rickless , and Wilson For alternative schemes for cataloguing interpretations, see Hatfield and Newman and Nelson For an anthology devoted largely to the Cartesian Circle, see Doney For discussions of the role of truth in perfect knowledge, see Frankfurt and , Hatfield , Lennon , Loeb , and Newman and Nelson However, the existence of an external material world remains in doubt.
Descartes builds on a familiar line of argument in the history of philosophy, itself appealing to the involuntariness of sensations. The familiar argument is first articulated in the Third Meditation. Speaking of his apparently adventitious ideas sensations , the meditator remarks:. Though some such involuntariness argument has convinced many philosophers, the inference does not hold up to methodical doubt, as the meditator explains:.
We first examined this passage in regards to the Always Dreaming Doubt. That doubt raises the problem of the existence of external things.
This sceptical hypothesis explains why the familiar involuntariness argument fails: the inference presupposes exactly what is at issue — namely, whether involuntarily received sensory ideas are produced by external things, rather than by a subconscious faculty of my mind. Many philosophers have assumed that we lack the epistemic resources to solve this sceptical problem.
For example, Hume writes:. Interestingly, Descartes would agree that experiential resources cannot solve the problem.
By the Sixth Meditation, however, Descartes purports to have the innate resources he needs to solve it — notably, innate ideas of mind and body. Among the metaphysical theses he develops is that mind and body have wholly distinct essences: the essence of thinking substance is pure thought; the essence of body is pure extension.
This result allows Descartes to supplement the involuntariness argument, thereby strengthening the inference. As Descartes writes, this cause. It follows that my sensations are caused by external world objects — i. It remains to be shown that these external causes are material objects. That is, the cause is either infinite substance God , or finite substance; and if finite, then either corporeal, or something else. Descartes thinks he eliminates options a and c by appeal to God being no deceiver:.
This is a problematic passage. But unless each step of the argument is clearly and distinctly perceived, Descartes should not be making the argument.
On one kind of interpretation, Descartes relaxes his epistemic standards in the Sixth Meditation cf. Schmitt , f. He no longer insists on perfect knowledge, now settling for probabilistic arguments. Though no decisive texts support the interpretation, it does find some support. For instance, in the Synopsis to the Meditations , Descartes writes of his Sixth Meditation arguments:. And other texts are unfavorable to this interpretation. For example, in the opening paragraphs of the Sixth Meditation, Descartes considers a probabilistic argument for the existence of external bodies.
This is a puzzling dismissal, assuming Descartes has relaxed his standards to probable inference. The relaxed standards interpretation falls short for another reason. It leaves unexplained why Descartes cites a divine guarantee for the conclusion that sensations are caused by material objects.
Instead, Descartes is extending the implications of his discussion of theodicy in the Fourth Meditation to encompass further cases of natural belief — such beliefs deriving from our God-given cognitive nature. It was noted above Section 5. Suppose Descartes holds that there are further cases in which an all-perfect God would not allow us to be in error, in part because the beliefs in question arise naturally from our God-given cognitive nature.
And suppose the further cases involve a natural propensity to believe which cannot be corrected by our cognitive faculties. Given these assumptions, the resulting rule for truth would look something like the following:. Indeed, a number of texts indicate that he holds some version of premise 2. As will emerge, Descartes looks again to call on this more expansive rule in his effort to prove that he is not dreaming. Earlier, we noted another apparent problem in the Sixth Meditation passage wherein Descartes concludes that the external cause of sensation is something corporeal.
One of his premises cites a great propensity to believe, yet the propensity is not itself the irresistible compulsion of clear and distinct perception.
Does not the methodic procedure of the Meditations restrict Descartes to clear and distinct premises? By way of reply, distinguish a that my sensation has an external cause, and b that I have a great propensity to believe my sensation has an external cause. In context, the meditator lacks clear and distinct perception of a. However, the relevant premise of the argument as opposed to its conclusion is not a , but b. And there is no principled reason that the meditator cannot clearly and distinctly perceive this premise.
A final observation. Granting the success of the argument, my sensations are caused by an external material world. But for all the argument shows — for all the broader argument of the Meditations shows, up to this point — my mind might be joined to a brain in a vat , rather than a full human body.
For even at this late stage of the project, the meditator has not yet established himself to be awake — a line of inquiry to which we now turn. See also Friedman , Garber , and Newman On the respects in which the Sixth Meditation inference draws on Fourth Meditation work, see Newman By design, the constructive arguments of the Meditations unfold even though the meditator remains in doubt about being awake.
This of course reinforces the ongoing theme that perfect knowledge does not properly encompass judgments of external sense. The judgment that an external corporeal world exists is not strictly a judgment of external sense — as if knowing its existence simply by sensing it.
In the closing paragraph of the Sixth Meditation, Descartes revisits the issue of dreaming. He claims to show how, in principle — even if not easily in practice — it is possible to achieve perfect knowledge that one is presently awake. A casual reading of that final paragraph might suggest that Descartes offers a naturalistic solution to the problem i. The following remarks can be read in this way:. Mirroring our discussion in Section 7.
Taken at face value, this reply rules out a relaxed standards interpretation; it indeed rules out any interpretation involving a naturalistic solution to the problem of dreaming.
On closer inspection, the Sixth Meditation passage puts forward not a naturalistic solution, but a theistic one. How does his argument go? Recall, in the proof of the external material world Section 7.
The dreaming passage looks to have Descartes again invoking this rule. The passage opens with the meditator observing the following:. As the meditator says speaking of his apparently waking experience :.
The cases like these to which Descartes refers look to be those where conditions i and ii are both satisfied. For everyone admits that a man may be deceived in his sleep. Whether in waking or dreaming, the Fourth Meditation theodicy has God allowing us to make judgment errors, provided that they are correctable.
Descartes is committed to holding that when our perception is confused, we can in principle come to discover the confusion — even if not easily. When we lack clear and distinct perception, we are at fault not God for any resulting judgments, in part because we can discover that our perception is confused.
Descartes needs it that the same principle holds even while dreaming. And again, nearly the entirety of the Meditations unfolds under the supposition that, for all we know, we may presently be dreaming. For the case at hand — i. Evidently, Descartes thinks so, as he tells Gassendi:. To the contrary, the Sixth Meditation treatment of the Now Dreaming Doubt closes with a concession that his solution is perhaps more theoretical than practical:.
Methodical doubt should not be applied to practical matters. Descartes holds that our judgments about our own minds are epistemically better-off than our judgments about bodies.
The confusion is clearly expressed Descartes would say in G. In epistemological contexts, Descartes underwrites the mind-better-known-than-body doctrine with methodical doubt. For example, while reflecting on his epistemic position in regards both to himself, and to the wax, the Second Meditation meditator says:.
Other reasons may motivate Descartes as well. He may take the doctrine to be closely allied to a representational theory of sense perception. Accordingly, our sense organs and nerves serve as literal mediating links in the causal chain generating perception: they stand between both spatially and causally external things themselves, and the brain events occasioning our perceptual awareness cf.
In veridical sensation, the objects of immediate sensory awareness are not external bodies themselves, nor are we immediately aware of the states of our sense organs or nerves. Descartes indeed holds that the fact of physiological mediation helps explain delusional ideas, because roughly the same kinds of physiological processes that produce waking ideas are employed in producing delusional ideas:. Various passages of the Meditations lay important groundwork for this theory of perception.
For instance, one of the messages of the wax passage is that sensory awareness does not reach to external things themselves:. This is an important basis of the mind-better-known-than-body doctrine.
In the concluding paragraph of the Second Meditation, Descartes writes:. The understanding of ideas as the only immediate objects of awareness arises in a number of texts. Complicating an understanding of such passages is that Descartes scholarship is divided on whether to attribute to him some version of an indirect theory of perception, or instead some version of a direct theory.
In this act of demolition and reconstruction, Descartes felt it would be a waste of time to tear down each idea individually. Instead, he attacked what he considered the very foundation: the idea that sense perception conveys accurate information. He developed several arguments to illustrate this point. In the Dream argument, Descartes argues that he often dreams of things that seem real to him while he is asleep. In one dream, he sits by a fire in his room, and it seems he can feel the warmth of the fire, just as he feels it in his waking life, even though there is no fire.
Likewise, in the Deceiving God and Evil Demon arguments, Descartes suggests that, for all he knows, he may be under the control of an all-powerful being bent on deceiving him. In that case, he does not have a body at all but is merely a brain fed information and illusions by the all-powerful being. Fans of the Matrix films may recognize this concept. Only then does he mention that 'to these reasons for doubting I recently added two very general ones' ibid.
It is clear that, in Descartes view, sensory knowledge had been thoroughly undermined before the sceptical hypotheses were introduced. And we can't regain our faith in our senses until we have shown how all these local sources of error can be corrected for and eliminated, a task which Descartes undertakes in the Sixth Meditation.
I conclude that the sceptical hypotheses play a secondary role in Cartesian scepticism. Its primary motor is the demand for certainty and that, together with well known facts about our fallibility, is quite sufficient to undermine the great majority of our beliefs. The sceptical hypotheses are needed only to deal with a special class of highly general beliefs: they make room for a doubt about the existence of an external world which, when combined with the demand for certainty, should suffice to destroy our faith in it.
So the task of establishing the coherence of the sceptical hypotheses matters much less to the Cartesian sceptic than that of motivating the demand for certainty. I think the latter, at least, can be done and I will attempt it with the resources available to Descartes in the last section. Descartes tells us that he has gone to great trouble to formulate the strongest form of scepticism so that by answering it, he can rid us of the sceptic for ever Descartes And what most obviously distinguishes Cartesian scepticism from its ancient predecessors is precisely its use of the sceptical hypotheses Burnyeat But we should not think that Descartes has invented a new, more powerful kind of doubt, unavailable to the ancients.
The sceptical hypotheses do not raise doubts of a kind we never had before; rather they extend the old sceptical doubts as far as they can possibly go.
The strongest doubt is just the most extensive doubt and the mechanism for generating this doubt is a traditional one: pointing out the possibility of error.
This mechanism is no more powerful than the demand for certainty which lies behind it. For now, we should be impressed by how little else the Cartesian sceptic need assume once the demand for certainty is in place. This infallibilist demand has often been associated with a foundationalist conception of human knowledge which portrays properly justified belief as the product of an inference from a class of propositions of which we are certain e.
Perhaps Descartes is a foundationalist but all the Cartesian sceptic needs is the requirement that we have a conclusive grounds for each of our beliefs and the observation that our grounds are always inconclusive. He need presuppose nothing about the theoretical structure or character of these grounds. What matters is simply whether they are conclusive or not. Hume's Misreading of Descartes.
Hume begins the section of the First Enquiry entitled 'Of the Academical or Sceptical Philosophy' with the following description of Cartesian scepticism:. It recommends an universal doubt, not only of all our former opinions and principles, but also of our very faculties; of whose veracity, say they, we must assure ourselves, by a chain of reasoning, deduced from some original principle, which cannot possibly be fallacious or deceitful.
But neither is there any such original principle, which has a prerogative above others, that are self-evident and convincing: or if there were, could we advance a step beyond it, but by the use of those very faculties, of which we are supposed to be already diffident. The Cartesian doubt therefore, were it ever possible to be attained by any human creature as it plainly is not would be entirely incurable; and no reasoning could ever bring us to a state of assurance and conviction upon any subject.
Hume In Hume's view, Cartesian scepticism has three elements a the demand that our use of any belief forming faculty be justified without prior reliance on that faculty b the demand that this justification give us certainty that the faculty in question is veracious or reliable and c the demand that all such justifications be based on a single foundational and self-evident principle.
In this passage, Hume means to be putting Cartesian scepticism to one side so he can raise his own, rather different sceptical problem. He rejects the three part demand which he associates with Cartesian scepticism and he does so by rejecting the first demand which is implicit the other two , the idea that we should not employ any cognitive faculty until we have first assured ourselves of its veracity.
But, as we shall see, Hume is wrong to attribute this idea to Descartes. In fact, Descartes and Hume share much the same conception of what a reasonable method of belief formation must be like and the conception which they share is fundamentally infallibilist. On Hume's interpretation, a Cartesian doubt can be raised prior to any reasoning and inquiry: it requires no grounds whatsoever.
But this fails to make sense of Descartes' text. Consider the following statement about beliefs based on clear and distinct perceptions:. If this conviction is so firm that it is impossible for us ever to have any reason for doubting what we are convinced of, then there are no further questions for us to ask: we have everything that we could reasonably want. What is it to us that someone may make out that the perception whose truth we are so firmly convinced of may appear false to God or an angel, so that it is, absolutely speaking, false?
Why should this alleged 'absolute falsity' bother us, since we neither believe in it, nor have even the smallest suspicion of it? Here Descartes is insistent that we can't induce a doubt about a belief that was based on the method of clear and distinct ideas without discovering some grounds for doubt: we must employ some method of reasoning even the very one in question in order to get a doubt going. Hume distinguishes ' antecedent' scepticism from another form of scepticism which is ' consequent to science and enquiry' Hume Real doubts, the kind of doubts the sceptic seeks to generate, are consequent on inquiry, not antecedent to it.
They arise once we begin thinking and reasoning. Hume is surely right that consequent scepticism is the real threat to belief; he is wrong only in failing to see Cartesian scepticism as consequent. Descartes never claims blankly that our beliefs may be false, that our methods of belief formation might lead us astray; he always tells a story, based on what he takes himself to have learnt of the world by using those very methods, about how reasoning involving them may actually have led us astray.
Even the evil demon hypotheses works as a sceptical device for Descartes in so far as it does because he takes himself to know that there are powerful spiritual beings, as the brain in a vat hypothesis works for us because experience has taught us about the physical basis of our mental lives.
Furthermore, Descartes' response to scepticism makes sense only if his scepticism is of the consequent variety. The passage about 'absolute falsity' just quoted occurs in the Second Replies where Descartes is rebutting the allegation that he was 'guilty of circularity when I said that the only reason we have for being sure that what we clearly and distinctly perceive is true is the fact that God exists, but that we are sure that God exists only because we perceive this clearly' Descartes Descartes denies that doubt about what we clearly and distinctly perceive is psychologically possible at the time at which we are clearly and distinctly perceiving it : doubt can arise only in retrospect when we come to reflect on how we formed this belief, a process of reflection which will inevitably employ the very method in question.
The point of proving God's existence is to quiet any such retrospective doubts by establishing that the method of clear and distinct ideas is self-confirming. We can use the method to prove the existence of an omnipotent and benevolent deity and God's existence in turn guarantees that this method is reliable.
Were Cartesian scepticism of the antecedent variety, the fact that our fundamental methods of belief formation are self-confirming would mean nothing: a completely erroneous method e. But a scepticism which is 'consequent to science and inquiry' may be answered in this way.
And, for Descartes, this should soothe any doubts about it. Humean Scepticism. Hume makes fun of the idea that we should 'have recourse to the veracity of the Supreme Being in order to prove the veracity of our senses' Hume ; he thinks Descartes' theological reasoning can deal neither with the antecedent, nor the consequent sceptic and it is hard to disagree. Hume then deploys several different sceptical arguments which seek to demonstrate that our belief forming processes are indeed self-undermining.
These arguments form the substance of Humean scepticism. Like Descartes, Hume himself is no sceptic [6] but like Descartes, he deploys sceptical reasonings in order to teach us something about belief.
The lesson he has to teach us - that belief is not governed by reason [7] - is not Descartes' but his way of addressing the issue, by means of consequent scepticism, is remarkable similar. Before looking at the details of Hume's sceptical argument, I want to articulate the conception of rational belief he shares with Descartes. For both of them. The most controversial element here is 3 , the idea that the subject cannot feel justified in having a given belief, in claiming knowledge, unless it seems to him that he has a conclusive reason for that belief.
Descartes distinguishes knowledge from mere conviction as follows:. The aim of his war against the sceptic is precisely to turn our convictions into knowledge. Hume has a similar notion of knowledge, a similar conception of the aim of rational belief. Indeed the first of Hume's sceptical arguments is meant to turn on nothing more than the fallibility of our belief-forming mechanisms.
Scepticism about Reason and the Senses. In the section of the Treatise entitled 'Of Scepticism With Regard to Reason', Hume attacks the very citadel of reason - deductive inference taken to include mathematical reasoning - but not by requiring some antecedent proof that deductive inference is a reliable cognitive mechanism.
Who would be surprised to find that we couldn't establish the veracity of deductive inference without making use of deductive inference? Instead, Hume allows us to employ deductive inference ab initio and then argues that it undermines itself.
Hume's line of thought goes as follows: once we have experienced the fallibility of any form of reasoning, deductive or inductive, reason itself requires us to make a judgement about how likely that reasoning is to deliver the right result 'as a check or controul on our first judgement or belief' Hume This higher-order judgement is itself known to be fallible on similar grounds and so we must make a further judgement about how likely it is that our assessment of the chance of error will be correct before we can reach any conclusion at all:.
But this decision, though it should be favourable to our preceding judgment, being founded only on probability, must weaken still further our first evidence, and must itself be weakened by a fourth doubt of the same kind, and so on in infinitum ; till at last there remain nothing of the original probability, however great we may suppose it to have been, and however small the diminution by every new uncertainty.
Hume concludes that reason subverts itself. This argument has great generality: it applies to any form of reasoning of which we have had enough experience to realise that it is fallible. But it rests on some rather dubious probabilistic reasoning and by the time Hume came to write the Enquiry , it had been dropped in favour of other sceptical arguments of rather narrower scope but with a similar form.
Take the habit of basing belief on experience. Hume attaches no great significance to the facts of sensory illusion which are. There are other more profound arguments against the senses, which admit not of so easy a solution. These remarks might seem put a great distance between Hume and Descartes, at least on my reading of Descartes. But no; Hume asserts that sensory fallibility is not worrying only because he thinks we can always correct for it.
Descartes would agree; he spends much of the Sixth Meditation telling us how to avoid sensory error altogether.
This is no more than a pious hope on both their parts. It is hard to see how, even in a case where we put our minds to it, we could eliminate all possible sources of local perceptual error; a fortiori in the generality of cases, given the constraints on our time and imagination. Putting this to one side, what is the 'more profound argument' Hume mentions? It is based on an assumption which Hume thinks the 'slightest philosophy' will confirm, namely 'that nothing can ever be present to the mind but an image or perception, and that the senses are only the inlets, through which these images are conveyed, without being able to produce any immediate intercourse between the mind and the object'.
Given this assumption, Hume's sceptical reasoning runs as follows:. It is a question of fact, whether the perceptions of the senses be produced by external objects, resembling them: how shall this question be determined? By experience surely, as all other questions of a like nature. But here experience is, and must be entirely silent.
The mind has never anything present to it but the perceptions and cannot possibly reach any experience of their connection with objects. The supposition of such a connection is, therefore, without any foundation in reasoning. Humean scepticism about the senses is clearly consequent. The Humean sceptic is not requiring, in advance of any reliance on sensory experience, that we justify such reliance by ruling out the possibility of illusory experience.
Rather, he is using sensory experience to undermine sensory experience as follows. Having begun by basing your beliefs on sensory experience correcting it with a bit of inductive reasoning you quickly learn e.
So by what means do you know of such external items?
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