You are here

Series I

Lecture 10: The Freedom of Assent in Descartes and Hume

What is the relation between belief and will, or more generally, between belief and the conative side of our nature? On this question there is an interesting conflict of opinion between Descartes on the one side and Hume on the other. It is convenient to begin with Hume's view (reversing the historical order) because it is a very natural and plausible one.

In a well-known passage in the Appendix to the Treatise of Human Nature1 Hume says plainly that belief is something involuntary. He is arguing against the theory that believing consists in adding some other idea to those which are already before one's mind. His answer to it is this: ‘The mind has the command over all its ideas, and can separate, unite, mix and vary them, as it pleases; so that if belief consisted merely in a new idea annexed to the conception, it would be in a man's power to believe what he pleased.’ He obviously regards this as a reductio ad absurdum of the theory which he is criticizing. He goes on to say quite explicitly that belief consists in ‘something that depends not on the will’ and that it arises ‘from certain determinate causes and principles of which we are not masters’.

Assent, then, according to Hume, is something wholly involuntary. We may illustrate his view by an example which he uses elsewhere, about flame and heat. If I see a flame over there, on the far side of the room, I cannot help believing that the flame is hot. I cannot prevent the idea of ‘heat over there’ from presenting itself to my mind in a lively or forceful manner. And if the idea does present itself to my mind in this lively or forceful way, that is the same as saying (in Hume's view) that I believe it or assent to it. So in a case like this, I just have to assent to the proposition ‘That flame over there is hot’; I cannot help it. I have no choice about it. Descartes, however, in an equally celebrated passage in the Meditations (Meditation IV)2 appears to reject this doctrine quite flatly. Descartes' word for assent is ‘judgement’. (Sometimes he calls it ‘affirming or denying’.) And the whole point of Meditation IV is to maintain that judgement is an act of free will. It might seem to follow from this that it is in our power to assent to whatever we please—just what Hume denies.

I am not sure whether Descartes does want to go quite as far as this. In actual fact, at any rate, it seems perfectly clear that we cannot assent to any proposition we please, just by an act of will here and now. Consider the proposition ‘Pigs have wings’. Is it really in one's power to assent to this proposition just by an act of free choice? Or again (to alter Hume's example a little), suppose you see a house which is on fire. You look into a room from outside, through the window, and see the furniture and the floor blazing, and hear the flames crackling. Is it in your power to assent to the proposition ‘the room is confortably cool’? You may very much wish that you could, because you would like to save a valuable picture which is hanging on the wall. But obviously you cannot assent to this proposition, however much you might wish to. On the contrary, you cannot help believing that the room is intensely hot.

Nevertheless, it is sometimes possible to induce oneself to assent to a proposition by a long series of voluntary efforts, even though it is not in one's power to assent to it by a single act of will here and now. To put it another way; belief can be voluntarily cultivated, at least sometimes, though it cannot be instantaneously produced just by a single fiat of will. This is why people sometimes request us or entreat us to believe things. When someone says ‘I never meant to do it, please do believe me’ (or even ‘You have got to believe me’, ‘You must believe me’), perhaps he is requesting or commanding something which is at the moment quite impossible. The story he has told us may be so extraordinary that we just cannot accept it here and now. Nevertheless, we may manage to accept it later if we try hard enough and long enough. Indeed, he himself might say ‘Please try to believe me’.

The important point here is that the direction of our attention is to a considerable extent under our voluntary control. For example, it may be difficult to believe an undergraduate's story when he says he fell asleep in the train on the way back from London, missed the connection at the junction, and woke up to find himself at Bristol instead of Oxford. Still, we reflect afterwards, he has told us the truth more often than not on past occasions, and on this occasion he told his story with an air of ingenuous sincerity. He is not a very good actor either, as we saw from his performance in the College play last term. And after all, people do fall asleep in trains sometimes.

In other words, what we do is to direct our attention to the favourable evidence, the evidence for the proposition we were asked to believe, and avert our attention from the evidence against it. This is something which we can voluntarily do, if we try hard enough and go on trying. And as a result, we may be able in the end to assent to the proposition without any difficulty, though it was quite beyond our power to do so at the beginning. Thus assent may be voluntary in the long run, at least sometimes, even though in the short run it is quite beyond our voluntary control.

You may think that the procedure I have described is indeed a charitable one (at least in this example), a case of trying to ‘believe the best’ of another person and succeeding; but you may also think that from an intellectual point of view it is somewhat disreputable. The point is, however, that this procedure—disreputable or not—is sometimes effective. So in some cases, at least, it is in a man's power to ‘believe what he pleases’, at any rate in the long run; and therefore Hume must be wrong when he says, without any qualification, that belief is something ‘that depends not on the will’. And Descartes is at least partly right when he says that judgement (assent) is an act of will. At any rate, he is right in maintaining that assent is to some extent under our voluntary control, in the long run even if not immediately; and we still have to admit that he is right about this, even if we reject his ultra-libertarian conception of the will.

I will just add that the process of voluntarily directing our attention is not always an intellectually disreputable or unreasonable one. By directing our attention to the favourable evidence, we may discover that there really is a good deal more evidence for the proposition than there seemed to be at first sight. We may be led to recall relevant facts which had not previously occurred to us, for example, that the undergraduate is an unusually sound sleeper, so that his story of not waking up at the junction might quite possibly be true.

What is intellectually disreputable is to direct your attention in such a way that you end by forgetting about the unfavourable evidence altogether. One ought to direct attention to the unfavourable evidence too; and then one may find that there is also more of that than one supposed.

But when Descartes maintains that assent is an act of will, what chiefly interests him, of course, is the negative side of this doctrine: not so much that it is in our power to assent as we choose, but that it is in our power to withhold assent as we choose. The important point about this ‘freedom of judgement’, in his eyes at least, is that it is a freedom to suspend judgement. The only limitation on it is that we cannot help assenting to propositions which we ‘clearly and distinctly perceive to be true’. We do have to assent to propositions which are self-evident. It is not so much that a man can believe what he likes; it is rather that (with this exception) he can always refrain from believing, if he likes. In all other cases, however plausible a proposition may be, however strongly or forcefully or vivaciously it presents itself to one's mind (as Hume would put it), one can always suspend judgement about that proposition, and just consider it in a neutral way, neither accepting it nor rejecting it. This is the kind of ‘freedom of judgement’ which Descartes is most anxious to maintain; and this is the most important part of his doctrine that assent is a matter of free will. If assent is a matter of free will, we are always free to refuse assent as well as to give it, except when the proposition we are considering is one which we clearly and distinctly perceive to be true.

This doctrine is an essential precondition for Descartes' Method of Doubt. We obviously cannot use this method unless it is in our power to suspend judgement about many propositions which we ordinarily believe. Descartes thinks that if we are able to withhold assent, by a voluntary effort, it is always in our power to avoid assenting erroneously. When we do fall into error it is our own fault. We need not have assented to a proposition which turns out later to be false.

A consequence of this, to which Descartes himself attaches importance, is that God is not responsible for our errors, whereas we should have to say that God is responsible for them, if we did not have this freedom to assent or to withhold assent as we choose. God is no more to be blamed for our erroneous assents than for our immoral actions. In the one case as in the other, it was in our power to refrain from making the wrong choice. In either case, the responsibility is ours. Each of us is personally responsible for his beliefs, as he is for his actions; whereas, if Hume were right, the notion of personal responsibility would have no application to beliefs at all.

From this, again, a further conclusion has sometimes been drawn, though not by Descartes himself: namely, that we deserve to be chastised for our intellectual errors, no less than for our moral delinquencies, and that it is no excuse in either case to say ‘I couldn't help it’. This is a most alarming contention, which could easily be used to justify all sorts of political and religious persecution. We may hope, for Descartes' sake, that it does not really follow from his doctrine of the freedom of assent. I shall return to this question later.3

But is it always in our power to withhold assent from propositions which are not self evident? In the example mentioned before about the burning house, is it in our power to abstain from assenting to the proposition that the room full of names is very hot? Can we help believing this, whether we like it or not? Can we suspend judgement about it, however hard we try? To take a less exciting example, can we help believing that the wall over there is hard? It may seem obvious that we cannot.

But even if we are incapable of withholding assent from these propositions here and now, there is still something which we can voluntarily do. We can train ourselves by degrees to suspend judgement about the whole class of inductively-supported propositions concerning matters of fact, propositions which acquire their ‘force’ or ‘vivacity’ (as Hume would put it) from a long experience of ‘constant conjunctions’. Descartes could still maintain that in the long run, though not immediately, it is in our power to withhold assent even from such propositions as these. After all, as Hume himself admits or indeed insists, these inductively-supported propositions are not logically necessary. It is conceivable that they might be false. Not only that. Some propositions supported by pretty strong inductive evidence do in fact turn out to be false, even though they present themselves to our minds with a ‘feel’ of forcefulness or vivacity, for example, the celebrated propositions that all swans are white; or that no creature with fur lays eggs (the duck-billed platypus does); or that what looks like water is water (it may be a mirage). Nor does Descartes claim that his Method of Doubt, which requires such suspense of judgement, is an easy one to use. On the contrary, he insists himself that a considerable amount of voluntary effort is required and has to be continued over quite a long period of time.

We should also notice that it is only suspense of judgement which Descartes is concerned with, not suspense of action. He is not recommending us to follow the example of the ancient sceptic Carneades, who had to be led about by the hand, to prevent him from walking into fires or over cliffs. And surely it is in our power to act as if a proposition were true without assenting to it, and even to act resolutely as if it were true. No one would deny, of course, that it is in our power to act so, when the proposition is one which we have no inclination to believe. This is something which actors and hypocrites manage to do quite easily. But Descartes maintains that it is in our power to combine these two attitudes—suspense of judgement and a decision to act ‘as if’—where the proposition is one which we have been in the habit of believing all our lives, for example, the proposition that walls are hard, or that dogs bite. He says that it is in our power, though it is not at all easy. We may notice that the same is said by mystics about the ‘spiritual exercises’ which they recommend; and indeed the Cartesian Method of Doubt could itself be regarded as a kind of ‘spiritual exercise’.

The Relevance of Some Psychopathological Phenomena

Before we decide that Descartes is mistaken, perhaps we might do well to consider certain phenomena of psychopathology, which do at least show what human nature is capable of, in the way of withholding assent from propositions which most men believe. In this respect, human nature is capable of more things and stranger things than common sense philosophers suppose, and even than Hume supposes.

There are propositions which the ordinary person might say he cannot help believing, for example the proposition that other human beings have thoughts and feelings as he has himself. And yet in some forms of mental disease people do refrain from assenting to these ‘obvious’ propositions. They are quite seriously not convinced that other human creatures are conscious beings, who have thoughts and wishes and feelings and sense-experiences. Or again, they are not convinced that walls are solid or even (sometimes) that there is a material world at all. Indeed, they sometimes go even further than Descartes recommends when he is describing his Method of Doubt. They not only suspend judgement about these propositions, but refrain at least sometimes, from acting as if they were true (for example they treat another human organism as if it were not conscious).

So Hume must be wrong if he thinks, as he apparently does, that assent to such propositions is absolutely unavoidable, that no-one can help believing them—whatever difficulties we may have, in our philosophical moments, in finding any good reason for doing so. For here are people who do not believe these propositions, but are in a state of suspended judgement about them. To these people it seems a perfectly serious possibility that these ‘obvious’ propositions might be false.

Of course, their attitude of suspended judgement is not altogether the same as the one Descartes has in mind. When such people refrain from assenting to these propositions which everyone else believes, their suspense of judgement is not a matter of conscious choice. It is not an exercise of what Descartes calls ‘free will’. So far as their consciousness goes, they just find themselves unable to assent to these propositions which everyone else believes. It is not just that they cannot help suspending judgement about them; they cannot help suspecting that these propositions may very well be false. Their non-assent, then, is not something consciously and freely decided on; and in that important respect it differs from the non-assent (or suspense of judgement) which Descartes is talking about, the suspense of judgement which is an essential part of his Method of Doubt.

But perhaps this is not the whole story. First, we may point out that according to some theories at any rate (theories of the psychoanalytical type) this pathological suspense of judgement, though we cannot call it voluntary, is not wholly involuntary either. There is a sense in which these people suspend judgement (withhold assent) because they want to, though this ‘want’ is an unconscious one, that is, a desire which they have but are unaware of having. They want to escape from what other people call ‘the real world’—the world in which there are things and persons independent of oneself, things and persons to which one must adapt oneself practically, and also emotionally, a process which is often troublesome and sometimes very painful. So they want this world of things and persons to be something whose existence is uncertain and questionable. Thus there is a sense in which they withhold assent from these ‘obvious’ propositions because they prefer to withhold it, though this preference is not a matter of conscious choice.

‘Be Mad in Order to Be Wise’

Descartes himself, of course,—unlike Leibniz—had no conception of unconscious or even subconscious mental processes or states. That is one of the major weaknesses of his philosophy of mind. Still, these pathological cases are relevant to his doctrine of the Freedom of Assent. As I have said already, they do at least show—contrary to the view of Hume and of some modern common sense philosophers—that human beings really are capable of withholding assent from propositions which most people believe with complete conviction. Moreover, it seems that motivation has something to do with this suspense of judgement. There is at any rate something conative or volitional about the non-assent which occurs in these pathological cases.

Well, what these mentally diseased persons achieve from unconscious motives (motives they are not themselves aware of, and are even unable to be aware of) we might be able to achieve by conscious choice and effort. And what they achieve from interested motives, from a desire to ‘escape from reality’, we might be able to achieve from disinterested ones—from a desire to find which of the propositions we ordinarily assent to are worthy of assent, or can be reasonably assented to.

There is something resembling madness in the Cartesian suspense of judgement. Critics of Descartes are right in pointing out that his Method of Doubt does require us to suspend judgement about propositions which all sane people believe in the ordinary affairs of daily life. Nevertheless, the difference of motives (between the insane persons we have mentioned and the Cartesian doubter) is after all rather important. Descartes' motive is a desire to know: the insane person's motive is a desire not to. And another important difference, as I have said, is that Descartes consciously decides to suspend judgement, in a wide-awake manner, well aware of why he does it; whereas the insane person suspends judgement without being aware of why he does it, and has no conscious control of his assenting or non-assenting.

If you like paradoxes, what Descartes says is ‘Be mad in order to be wise’: not in order to escape from reality (or from disagreeable duties to your neighbour), but in order to find out, if you can, what sort of a real world there is, and what propositions can be reasonably believed about it. The best way, he says, of achieving these aims is to become conscious of your freedom in assenting: to realize, by actually doing it, that you are free to withhold assent if you choose; that you need not give your assent to any proposition if you find no good reason for doing so. I see nothing silly in this programme; and I think that when Descartes emphasizes this autonomy of rational beings, their freedom to assent or not as they see fit, he has put his finger on something important, which empiricist philosophers have tended to neglect.

Locke, it is true, does seem to agree with Descartes on this point. The ‘Ethics of Belief’ which he states in Book IV of the Essay seems to presuppose a theory of the freedom of assent. But later empiricists, for the most part, have not paid much attention to this part of Locke's philosophy, or have rejected it. We have seen that Hume explicitly rejects the doctrine of freedom of assent, and maintains on the contrary that belief is something wholly involuntary. We have also seen that Newman (whom one may count as an empiricist) makes a brilliant and savage attack on Locke's version of the Cartesian doctrine.4 If I may continue to talk about the history of Philosophy for a moment, I should like to suggest that this issue about the freedom or non-freedom of assent has some bearing on a complaint which has sometimes been made against the empiricist philosophy—the objection that the empiricists conceive of the human mind as ‘purely passive’. There is a good deal of confusion in this criticism. One may point out, for example, that the antithesis between ‘active’ and ‘passive’ is a somewhat slippery one, and moreover that both ‘active’ and ‘passive’ are highly emotive words as these critics of empiricism use them.

Nevertheless, this traditional objecton to empiricism is not wholly pointless. The empiricists have not always been clear about the distinction between the mental processes which just go on in us automatically, and those which are rationally and consciously controlled. To put it in an exaggerated way, they tend to regard the human mind as if we were half asleep all the time. So we are, much of the time. We do spend a good part of our lives behaving, and thinking, in a more or less habitual way.

But we are not always in this condition. It is in our power to wake up, to become self-conscious and clearly aware of what is going on in us (or at least of some of the things which are going on in us) and to criticize and evaluate it: to ask ourselves what reason there is for believing something we find ourselves believing, or what good there is, either moral or prudential, in some action we find ourselves doing or about to do. And then, if we see fit, we can decide, at least sometimes, to give up this belief and either suspend judgement or adopt some other belief instead; and similarly, to abandon this action, and either do nothing, or do something else instead. Moreover, these decisions are sometimes effective.

It is as if we had the power of intervening, consciously and rationally, in our own mental processes, and of altering the course they take. And this is one of the excuses for the talk about ‘two selves’, a ‘higher’ self and a ‘lower’ self, which bothers some philosophers so much. Still, everyone knows that we can do the things I have just been trying to describe, however difficult it is to talk sense about them. And my suggestion is that the empiricists have on the whole tended to emphazise these facts too little; whereas the rationalists—or at any rate Descartes and Leibniz— and Kant too, who is a rationalist in his moral philosophy—have perhaps emphasized them too much.

The relevant antithesis, however, is not that between ‘active’ and ‘passive’ (as in the traditional criticism of empiricism which I mentioned). It is rather the antithesis between two sorts of activity, automatic and unchosen activity, and reasonable self-conscious activity, when the course of our thoughts and of our actions is controlled by conscious decisions.

Or again (if I may continue a little longer with these rather high-flown considerations) perhaps we might put the point this way: There are two types or levels of ‘autonomy’ or ‘freedom’ in the human mind, and consequently two types or levels of ‘responsibility’. In the first, it is simply that the αρχη κινησεως is εν ημιν (as Aristotle puts it), ‘the cause of what happens is in ourselves’. We behave as we do because of our desires or our habits; we believe as we do because of our past experience of constant conjunctions, or because of our desires again, or because we have got into the habit of believing what our teachers told us.

But there is another sort of autonomy which we only have when we consciously decide what to do, and consciously decide what propositions to assent to. We may sometimes consciously decide to assent or to act unreasonably. But this sort of ‘chosen’ unreasonableness is something different from the unchosen unreasonableness which we display when we assent stupidly or act foolishly without being clearly aware of what is going on in us. Of course, we are responsible for these unchosen stupidities or follies or wrongdoings. These unchosen assents or actions were ours and we must take the blame for them. But if we assent or act ‘with our eyes open’, as a result of a conscious decision, we are responsible for our reasonableness or unreasonableness in a new way, or to a degree we were not before.

‘Clearly and Distinctly Perceived’

So far I have been arguing that there is a good deal to be said for Descartes' doctrine of the Freedom of Assent. But the use which he himself makes of it is another matter, or (if you like) the use which he recommends us to make of this freedom of assent which he claims we possess. Here he lays himself open to very serious criticisms, as recent philosophers have pointed out. According to Descartes, a reasonable person will assent only to those propositions which he clearly and distinctly perceives to be true. He will withhold assent from all other propositions (even though he may go on acting as if they were true, as a thinker he will suspend judgement about them). For this is the only way in which he can avoid assenting erroneously. What sort of proposition can be clearly and distinctly perceived to be true? Sometimes Descartes is thought to say that the only propositions in this privileged class are logically necessary ones.

He does, of course, lay great stress on the clearness and distinctness of mathematical propositions, and especially of the simpler sorts of mathematical entailments which can be comprehended without the aid of memory. But he does not really hold that logically-necessary propositions are the only ones which can be clearly and distinctly perceived to be true. Some contingent propositions are also admitted to this privileged class: for example the contingent proposition ‘I am now thinking’. There are also propositions (equally contingent) concerning the ideas which I have at present in my mind. These ideas may or may not correspond to anything in the extra-mental world, but at any rate it is evident that I do have them. Let us call these ‘inspectively-evident propositions’.

Thus he holds, I think, that there are two sorts of propositions which are clearly and distinctly perceived to be true. (1) logically necessary propositions, or rather those logically-necessary propositions which are simple enough to be grasped without the aid of memory. (2) inspectively evident propositions about one's own mental processes and about the ideas one has in one's own mind. And his view is that in order to avoid error, we ought to assent only to propositions which fall into one or other of these two classes, and that we ought to withhold assent from all other propositions—unless or until we can see that some of them follow logically either from a necessary proposition, or from an inspectively evident one, or from some combination of the two. This is his recommendation for the use we should make of the Freedom of Assent which he claims that we have.

But what makes this policy reasonable? Descartes' answer is, that it is the only one which will save us from assenting mistakenly. It is, so to speak, an insurance policy against error—and he claims that it is the only possible insurance policy for this purpose. We might be inclined to reply that it is reasonable, at least sometimes, to take the risk of assenting mistakenly. Taking this risk, and accepting the consequences, is sometimes the best way of finding out what the facts actually are. But let us suppose that we do wish to avoid error at all costs. Even so Descartes' recommendations for avoiding it involves him in very great difficulties.

Some Difficulties in Descartes' Argument

For we must ask how we know that we are liable to fall into error, if we do assent to propositions which we do not clearly and distinctly perceive to be true. Unless we do know this, or at least have good reasons for believing it, Descartes' insurance policy is pointless, and there is no reason for limiting our assents in the way he recommends. For example, how do I know that I run the risk of being mistaken if I assent to Hume's proposition ‘That flame over there is hot’? It is true we know a priori that this proposition may conceivably be false. Its falsity would involve no contradiction. That is, it is not a logically necessary proposition. And it is not an inspectively evident proposition either, as ‘There now appears to me to be a flame over there’ is. But though it may conceivably be false that the flame over there is hot, or even that there is a flame over there at all, it does not follow from this alone that either of these propositions is in the least likely to be false—as Moore has pointed out. If you claim that there is a finite probability of its being false, and therefore there is a risk of being mistaken if one assents to it, you must give grounds for making this claim.

‘Well’, you may say (as Descartes himself does) ‘Propositions of this sort, which I have believed in the past—empirical or contingent propositions going beyond what is inspectively evident—have quite often turned out to be false. So I run the risk of being mistaken again if I assent to such a proposition now.’ This argument is very plausible. But there are two difficulties in it. (a) How do you know that its premiss is true? (b) If it is, why should it be relevant to the conclusion (viz. that I am likely to be mistaken again if I go on assenting in the way I have in the past)?

Let us first consider the premiss. If you do know that you have held false beliefs in the past (have assented mistakenly)—as of course you do—you can only know this by memory. But according to Descartes' own principles, all memory judgements are fallible. No memory-proposition can be clearly and distinctly perceived to be true.

He is somewhat embarrassed about this point, because on the face of it memory is needed for all deductive reasoning except the very simplest. For example, to follow the reasoning in Pythagoras' theorem—to see that if something is a Euclidean right angled triangle, the square on the hypotenuse must be equal to the sum of the squares on the other two sides—you must remember the earlier steps in the argument in order to see that the conclusion is entailed by them. But he thinks this difficulty can be got over by training yourself to keep all the steps of the argument in mind at once (itself an inductive claim). And I think he does want to stick to his contention that all memory-judgements are fallible.

Now if they are, I cannot know that I have held false beliefs in the past. No doubt I am strongly inclined to believe this proposition about my own past beliefs. But after all, it is only a memory proposition, and I do not clearly and distinctly perceive it to be true. So according to Descartes' principles I ought to withhold assent from this proposition about my past beliefs. Nothing compels me to assent to it, however much I may be inclined to. So, if I am reasonable, should I not suspend judgement about it?

Thus the premiss of Descartes' argument—the proposition that I have often assented erroneously in the past—is one which he is not entitled to assert on his own principles. He can indeed assert that this proposition about his own past mistakes is being entertained by him, and also that he feels an inclination to believe it. For these are things which are inspectively evident. But he is not entitled to assert to the proposition itself, because it is a memory-proposition, and therefore not one which he can clearly and distinctly perceive to be true.

Moreover, in order to know that we have assented mistakenly in the past, we really need to use memory twice over. First we must be able to remember that we really did assent to a proposition p on some past occasion. But this is not all that we have to remember. For secondly, if I claim to know not only that I did assent to this proposition on some past occasion, but also that the proposition turned out to be false, I must remember that the actual facts were other than I had believed them to be.

To take an example of Descartes' own, he believed that a tower which he saw in the distance was round, because it looked round from the place where he was. He must be able to remember that he did believe this. But before he can assert that this was an erroneous belief, he must be able to remember that the tower turned out later to be square and not round at all. And here, we may notice, we should have to assume that some perceptual propositions—propositions about material objects (not just about sense-data) can be known to be true. To take another example, I myself used to believe that all rooks are black. How do I know that this belief of mine was mistaken? Because I remember seeing a pale-cream coloured rook one day on the top of Elsfield Hill.

So much for the premiss of Descartes' argument. He is not entitled to assert that he has often made mistakes in the past, if the class of propositions to which we may reasonably give assent is as restricted as he claims it is. For in order to assent that he has often made mistakes in the past (or even that he has ever made any mistakes at all) he must be able to remember what some of his past beliefs were, and also to remember that the facts turned out to be different from what he had believed them to be.

Descartes' Reliance on Induction

Now I turn to the second difficulty in Descartes' argument. However much I know about my own past mistakes, why should this knowledge be relevant to the conclusion Descartes wishes to draw—namely that if I give assent to similar propositions in future, I am likely to be mistaken again? The difficulty, from Descartes' point of view, is that this is an inductive argument, an argument from observed cases to unobserved cases. Because some past beliefs of sort A have turned out to be incorrect, it is likely that other beliefs of sort A will also be incorrect. That is the argument, and it is clearly an inductive one.

Now the trouble with an inductive argument, as Hume pointed out, is that the conclusion is not entailed by the premiss. There is no contradiction in supposing that the conclusion might be false although the premiss is true. And this is still so, when the conclusion takes the form of a probability statement, as it does here (some propositions of sort A have been false, therefore there is a probability that other propositions of sort A will also be false).

So here Descartes seems to be in a very awkward dilemma. This inductive proposition ‘Because past beliefs of sort A have sometimes been erroneous, there is a probability that future beliefs of sort A will sometimes be erroneous’—is not one which we can clearly and distinctly see to be true, since the premiss does not logically entail the conclusion. It would seem, then, that Descartes ought to withhold assent from it. Yet if he does, he can give no reason for what I called his insurance policy—his policy for avoiding error by confining his assent to propositions which he clearly and distinctly sees to be true.

If we are to refuse to assent to inductive arguments (on the ground that their premisses do not entail their conclusions) the fact that beliefs of sort A have often been erroneous in the past is no reason whatever for supposing that future beliefs of sort A are sometimes likely to be erroneous too. On the other hand, if Descartes is willing to accept inductive evidence as relevant in this case (when he is recommending a policy for assenting) he can have no good ground for refusing to accept it in other cases. And then the policy he recommends is too narrow. It cannot then be reasonable to assent only to logically necessary propositions and inspectively evident ones, and to withhold assent from all others.

I am not saying that there is anything inconsistent about the policy itself. But I am saying that it is inconsistent with the reason which he gives for it, because this is an inductive reason; and also (as I mentioned earlier) because the facts which he appeals to are facts about the past and require that we should assent to memory propositions, which we have no right to do if we follow the policy of assenting he recommends—and to some perceptual propositions too, for example ‘The tower is square, though it looked round from a distance’.

If I am right, it follows that his insurance policy for avoiding error is too narrow; and he has himself admitted this, first by assenting to memory-propositions about his own past errors, and secondly by assenting to an inductive argument from past errors to the probability of future ones.

So much for the way Descartes applies his doctrine of the Freedom of Assent, or, if you like, the way he recommends us to use the freedom of assent which he claims that we have. In recommending that we should withhold assent from (suspend judgement about) all propositions except those which we clearly and distinctly perceive to be true, he has too narrow a conception of reasonableness—too narrow a conception of what constitutes a good ground for assenting. We may have good grounds for assenting to memory propositions, perceptual propositions, and inductively-supported propositions—with greater or less confidence, according to the strength of the evidence. It is not true that the only good grounds we can have for assenting to a propositions are that it is either logically-necessary, on the one hand, or inspectively evident on the other.

Moreover, in the reasons he himself gives for recommending that we should limit our assents in this way, he assumes that inductive arguments can give good grounds for assent, and also assumes that some memory propositions and some perceptual propositions may be properly assented to: assumptions he cannot consistently make, if his own recommendations are correct.

Can We Be Reasonable All the Time?

But of course Descartes' doctrine of Freedom of Assent might be true, and important too, even though he himself mis-applies it. Nevertheless, there is one rather serious qualification to be made. Descartes is right in insisting that we do have the power of withholding assent from a proposition if we see no good reason for assenting to it. It is in our power to wake ourselves up and decide consciously whether to assent or to suspend judgement. But though we have this power, can we exercise it at all times? He seems to assume that we can, if only we will make the effort. ‘Just pull yourself together’ he seems to say ‘and everything will be all right.’

The trouble is, I think, that Descartes regards human beings as more mature and grown up, so to speak, than they actually are. We are not capable of maintaining ourselves continuously in this wide-awake and fully conscious state which he describes—neither with regard to our assents nor yet with regard to our actions—though we are capable of getting ourselves into it for short periods, and this is an important fact about us which empiricist philosophers have tended to neglect—despite Locke's remarks on the Ethics of Belief in Book IV of the Essay.

I said earlier (somewhat extravagantly perhaps) that empiricist philosophers tend to write of the human mind as if we were always half asleep. Descartes tends to make a different and to some extent opposite mistake. He seems to assume, not indeed that we are always wide awake, but that we could always be, by a mere effort of will. The trouble is that we can sometimes be wide-awake (more often that we actually are) but not always.

Nevertheless, it is important to emphasize that we do have the power of waking ourselves up and deciding consciously and autonomously whether to assent or not, even though we are not capable of maintaining ourselves in that state all the time. After all, we are rational beings, though it is beyond our power to be wholly rational all the time. But even if it were in our power to be wholly rational all the time, it still would not follow that there is anything morally blameworthy about assenting unreasonably (against the evidence or without regard to the evidence) or that we ought to be chastised for doing so.5 There is nothing wicked about such assents. It is however true, and important, that unreasonable assent is contrary to our long-term interest. It is to our long term interest to believe true propositions rather than false ones. And if we assent reasonably (i.e. in accordance with the evidence), it is likely that in the long run the propositions we believe will be more often true than false.

An Inconsistency in Hume

To return now to the conflict between Descartes and Hume concerning the Freedom of Assent: it is worth while to point out that though Hume does say that belief is wholly involuntary—‘depends not on the will’, arises from principles ‘of which we are not masters’—yet he is not wholly consistent about it.

First, what we may call his own philosophical practice seems to contradict his anti-Cartesian theory. If anyone ever went in for Cartesian doubt on the grand scale, surely Hume did. In his sceptical mood, he himself practises Cartesian suspense of judgement, perhaps even too successfully (for instance in Book I Part IV of the Treatise).

In that mood, he certainly does refrain from assenting to the propositions which he says elsewhere that we cannot help believing. And his motive is precisely the one Descartes recommends. He abstains from assenting to these propositions because he can find no good reason for assenting to them. And he confesses himself that his belief in them can only be restored by ‘carelessness and inattention’, or by returning to the activities and interests of ordinary life, such as playing backgammon or dining with his friends.6 These words seem to denote a slipping back out of the wide-awake and fully conscious condition in which Descartes thinks we have to be, if we are to exercise our freedom of assent.

Secondly, in his less sceptical moods Hume is willing to divide our beliefs about matters of fact into two classes. On the one hand, there are the beliefs which have strong inductive support, based on a long experience of constant conjunctions; on the other, there are beliefs which have very little inductive support or none at all.

He does not go so far as to call the first sort of beliefs reasonable ones, as we probably should. We should be inclined to say that they are reasonable in the inductive way, and should reject the assumption that the deductive criteria of reasonableness are the only ones. Nevertheless (in this less sceptical mood) Hume clearly does think that there is a distinction between sensible or sober or sane beliefs on the one side, and silly or superstitious beliefs on the other.

Not only that: he clearly thinks that it is better to hold sensible beliefs, those which have strong inductive support from past experience (of constant conjunctions), than to hold superstitious or silly ones which have very weak inductive support or none at all. Of course, it might be better to abstain from holding silly or superstitious beliefs—it might be better to withhold assent from propositions which have no inductive warrant—and yet we might be incapable of withholding it. Habit or education might be too strong for us. But clearly this is not what Hume thinks himself, at any rate in the Enquiry concerning Human Understanding. In the last four pages of the Enquiry.7 He offers us what one may call a policy for believing. So far as propositions concerning matters of fact are concerned, the policy consists in putting all one's money on inductive evidence; and the only a priori propositions we are allowed to assent to are deductively-established propositions about ‘quantity and number’. He does not just describe this policy, which he calls ‘mitigated scepticism’. He recommends us to adopt it. If so, he must surely think that it is in our power to refrain from assenting to propositions, unless and until we find that they have the kind of support which the policy requires.

He is now assuming (just like Descartes) that it is at any rate in our power to abstain from assenting if we choose. This policy for believing was part of a whole ‘way of life’, too—a way of life which he actually practised, and which helped to make him the admirable and charming person that he was. Hume, perhaps, was a bit of an Existentialist in this part of his philosophy.

The policy he recommends may or may not be a good one. Some of the beliefs he would regard as superstitions may have more to be said for them than he allows. But that is not the question we are discussing. The relevant point at present is merely that he does recommend a policy for assenting: and thereby admits that we do have that freedom to withhold assent from some propositions and give assent to others, which Descartes claims we have.

  • 1.

    Clarendon Press edition (ed. Selby-Bigge) pp. 623 fin.—4.

  • 2.
    Philosophical Works of Descartes (edited by Haldane and Ross, Cambridge University Press 1911), Vol. 1, pp. 174–7.
  • 3.

    P. 238, below.

  • 4.
    Grammar of Assent, ch. 6. See Lecture 6, above.
  • 5.

    See p. 225, above.

  • 6.
    Treatise (ed. Selby-Bigge), pp. 218, 269.
  • 7.
    Enquiries (Clarendon Press, Ed. Selby-Bigge), pp. 162–5.
From the book: