Descartes’ Meditations on First Philosophy 13

Abstract

Descartes’ Metaphysics of Nature and Mind—The Sixth Meditation (Part III)

Descartes’ Metaphysics of Nature and Mind—The Sixth Meditation (Part III)

I want now to consider the final three pages of the Sixth Meditation, that is, pp.68-70. For here we see very clearly how Descartes derives from his metaphysics of mind and its place in nature the crucial premise or assumption of the argument from dreaming and from the possibility of radical deception by an evil mind. This premise, you will recall, is that whether he is or is not asleep, the victim of an evil mind, or even a brain in a vat, Descartes is undergoing or having experiences and thoughts. Or, to put the assumption in another way, in both arguments Descartes assumes that there really is a passing of ideas through his mind in that sense of the phrase ‘passing through one’s mind’ which entails a real capacity to identify these ideas, to refer to them and ask of them whether they are or are not true, veracious, etc. Let us recall the passage in which Descartes outlines his views on how the mind relates, first to the brain, then to the body and finally, through the body, to the wider natural world:

… I perceive that the mind is not affected immediately by all the parts of the body but only by the brain or, perhaps, only by one small part of the brain, namely the part in which the common sense is said to be.1 Whenever this part is in the same state, it presents the same thing to the mind even though the other parts of the body may be in different states. This is proved by many experiences that need not be reviewed here. (p.68)

The bidirectional causal relation in which the mind stands to the brain is thus as intimate as it can be: any relation in which the mind stands to other things in the natural world is mediated by the brain. The mind is only at such and such a point in space and time because the brain is; and all causal relations in which the mind stands to other natural things pass through the brain.

This account of how the mind occurs in nature has two immediate and important consequences. Firstly, it renders the concept of a human being a derivative one. The full human being or human person simply is the causal unity of mind, brain and body. Secondly, it entails that thoughts (items in the mind) and brain events correlate well with one another. For it entails that different thought and experiences in the mind correspond one-to-one to different neuro-physiological events in the mind: different thoughts or experiences in the mind cause and are caused by different events in the brain. It must therefore be in principle possible to identify in the brain correlates of the thoughts in the mind, i.e., those brain events of which the thoughts are either the causes or the effects. It is in principle possible to read off what thoughts are going through an individual’s mind by tracking brain events.

It is not obvious that either of these consequences is true. Certainly, Leibniz thought that the second was not. Thus, he claimed that even if one enlarged the brain to the size of mill, such that one could walk around in it, one still would not see any thoughts. And if it is not possible thus to identify thought and experiences in the mind by correlating them with the brain events which cause or are caused by them, then the idea that one could define the concept of a human being as in effect a mind causally annexed to a brain and thence to a body must also be false. In other words, if the second is false, then so is the first. The notion of a human being or a human person cannot be construed as a composite, i.e., simply identified with the idea of the mind standing in a certain kind of causal unity with the brain, which is itself construed as standing in a certain kind of causal unity with the body. Rather, these latter concepts must be seen as derivative upon the idea of the full human being, i.e., distinguishable but not separable moments or aspects of the full, embodied human person.

Note that this would be in effect to concede that Aristotle was right about the mind: it is merely the form of the body, that is, a feature or property of the full human being which cannot exist except in unity with the physical body. Note, too, that it would be to say that the brain, while certainly the cause of thinking, does not itself think. The human being or human person is not identical with its brain; it merely has its brain. And the brain itself cannot be described as the place or site at which thoughts occur unless one means by this nothing more than that the brain is causally responsible for psychological attributes, dispositions and capacities of the human being. Or, to put this point in another way, it makes no sense to identify individual causal processes and events with individual thoughts and experiences; these latter must be seen as properties of the human person and not as properties of, or entities in, the brain of the person to whom they belong. Finally, it is important to note that this does not entail that there is absolutely no sense in which one cannot think of a human being or human person as a brain standing in causal interaction with its environment. The point is rather that there is no non-circular sense in which one can do this, i.e., no sense which does not itself presuppose the concept of the full human being or person. Every attempt to characterise the causal interaction of the brain with its body and the wider environment in a fashion which successfully picks this causal unity of brain and body out as a human being ends up tacitly characterising the interaction in terms which presuppose the concept of the full, embodied human being.

But neither these consequences of Descartes’ position nor what their falsity would entail are of primary importance here. Rather, for current purposes the most important consequence of Descartes’ conception of how the human mind occurs in nature is one drawn by Descartes himself. Thus, having outlined how the mind relates to brain and body – in effect, his conception of what it to be a full human being – , he goes on to say,

I also perceive that the nature of the body is such that no part of it can be moved by another part at a certain distance from it, unless it can also be moved in the same way by any of the parts in between, even when the more remote part does nothing. For example, in a cord ABCD, if one end of it D is pulled, the other end A will be moved in the same may as if one of the intermediate parts, B or C, had been pulled and the end D had remained unmoved. In a similar way, when I feel a pain in the foot, physics teaches me that that sensation occurs by means of the nerves that are spread through the foot and are stretched from the foot to the brain like cords; when they are pulled in the foot, they also pull the inner parts of the brain where they terminate, and they stimulate a certain motion there, which was established by nature to affect the mind with a feeling of what seems like a pain in the foot. Since these nerves have to pass through the leg, the thigh, the loins, the back and the neck to reach from the foot to the brain, it can happen that, even if that section of the nerves which is in the foot is not affected but only some other intermediate section, evidently the very same motion occurs in the brain as when the foot is hurt, from which it will necessarily follow that the mind feels the same pain. The same thing must occur in the case of other sensations. (p.68)

The paragraph begins with Descartes characterising, in very general terms, his conception of what it is to be a material thing. Although he does not mention his corpuscular theory of matter as such, he does mention a distinctive feature of it. This is Descartes’ famous, not to say infamous denial of action at a distance. All bodies are, by definition, extended. They thus have spatially arranged parts2 of which some, say, PA and PD, are at some distance greater than nought to one another. Let there be some kind of causal interaction between PA and PD. Then, claims Descartes, there are parts … PB , …. PC, … lying between PA and PD through which the causal interaction between PA and PD runs. It immediately follows from this3 that there must be an unbroken chain of contiguous parts between PA and PD across which the causal impact of the one upon the other is transmitted.

It follows, of course, from this conception of causality as requiring intermediary elements between non-contiguous causes and effects that if one of the intermediary parts between PA and PD were caused to act in precisely the way in which, say, PA had caused it to act, then the effect upon PD would be precisely the same as if PA had initiated the whole process. This point now permits Descartes to draw an important conclusion:

It is perfectly clear from these considerations that, despite the immense goodness of God, human nature, insofar as it is composed of a mind and body, cannot avoid being deceptive occasionally. For if some cause that is not in the foot, but in some other part of the body through which the nerves are stretched from the foot to the brain or even in the brain itself, causes the very same motion which is usually caused by a damaged foot, pain will be felt as if it were in the foot. Thus the sense is naturally deceived because, since the same motion in the brain must always trigger the same sensation in the mind and since it results much more frequently from some cause that harms the foot rather than from anything else, it is reasonable that it would always signal to the mind a pain in the foot rather than in any other part of the body. If it happens occasionally that dryness of the throat arises, not as it usually does because a drink is conducive to the health of the body but from some other contrary cause (as happens in the case of dropsy), it is much better that it would mislead in that case rather than always mislead when the body is healthy, and likewise for other examples. (pp.69-70)

According to Descartes, pain itself is a strictly physical phenomenon in which some injury stimulates nerves in the body to cause in the brain a pain sensation. This pain sensation then goes on to cause in the mind awareness of pain in the sense of direct and immediate knowledge that one has a pain in such and such part of the body, in Descartes’ example, the foot. Notice that on this account it immediately follows that creatures with brains but no minds can certainly feel pain; the idea that, as anti-Cartesian propaganda has persistently insinuated, Descartes regarded animals as not really capable of pain is just false. What animals are not capable of is self-conscious awareness of themselves as in pain, in particular, as having a pain in such and such part of their bodies. Notice, too, that this account suggests an explanation of why Descartes is so fascinated by the phenomenon of phantom limbs:4 he sees this phenomenon as providing corroborating empirical evidence for his metaphysical picture of how the human mind occurs in nature, namely, by standing in substantial union with the human brain.

But the important conclusion Descartes draws here is that “human nature, insofar as it is composed of a mind and body, cannot avoid being deceptive occasionally.” (p.69) In other words, the very way in which the human mind occurs in nature, namely, through substantial union with the brain, is responsible for the possibility and, as the phenomenon of phantom limbs demonstrates, sometimes the actuality, of a distinctive kind of error. This error consists in precisely the kind of scenario Descartes has imagined in more abstract terms immediately previously, where some part of the body PD is affected by some part PC lying between PA and PD in the manner in which PA would act through PC to affect PD but without actually being caused thus to affect PD by PA. And if this scenario is possible, then, so, too, is the scenario in which PD is affected in the manner for which PA is usually responsible without its being thus affected by any of the items usually responsible for this, whether PA itself or any of the intermediary parts … PB, …. PC, … . Thus, it suffices for the production of exactly the temporal series of thoughts and experiences in Descartes’ mind {…, I1, I2, I3, …} that the temporal series of neurophysiological events {…, B1, B2, B3, …} occur in his brain. And if this is so, then two kinds of radical deception become possible. In the first case, the usual causes of these brain events are imitated by a completely different set of causes whose only similarity with these usual causes is that they have this same set of affects on Descartes’ brain. This possibility is, of course, represented by the situation in which Descartes is dreaming or again, the victim of an evil computer scientist who has cut his brain out of his body, placed in an a life-sustaining vat and wired it up appropriately to a computer. In the second case, the temporal series of brain events {…, B1, B2, B3, …} has itself been imitated, say, by some series of events {…, B*1, B*2, B*3, …} which engenders in Descartes’ mind the same series of thoughts {…, I1, I2, I3, …} as is usually engendered by the series {…, B1, B2, B3, …}. This corresponds, of course, to the scenario of the evil mind who is radically deceiving Descartes.

So Descartes here derives the very possibility of radical global error and deception from his metaphysical account of how the human mind occurs in nature. He does not derive it from philosophically uncontaminated, neutral, everyday or commonsense intuitions about knowledge, perception and justification but rather from a highly theoretical, abstract philosophical theory about how our minds occur in nature. So precisely this picture of the human mind and its place in nature gives Descartes the crucial assumption he needs in order to show that, prior to determining whether any given perceptual experience he is now undergoing, hence currently before his mind, is or is not veridical, he must first determine, so to speak from within, whether it is a perceptual experience at all and not rather the product of some kind of global deception. As we know, when Descartes launches his argument from dreaming, he assumes that he can have thoughts and experiences in a dream in the very same sense in which he has them in waking life. And this assumption is, of course, carried across to the subsequent argument from the possibility of deception by an evil mind. Both arguments are carried by the assumption that whether he is or is not dreaming, whether he is or is not the victim of an evil mind, he can have things in his mind in just the same sense as in waking life, namely, as items he can bring before himself for interrogation. Descartes needs this assumption if he is to maintain that prior to determining whether a given perceptual experience is or is not veridical, he must first determine whether it is or is not a reliable perceptual experience rather than the product of sleep or a supremely powerful evil mind.

But what would it mean were this assumption false? What the falsity of this assumption would mean is that there were simply no room for the prior question of whether what Descartes has before his mind is or is not a perceptual experience, with all the intrinsic reliability of a perceptual experience. More precisely, there would be no room for the prior act of questioning and determining whether what Descartes has before his mind is or is not a perceptual experience. For there would be simply nothing in his mind in the requisite sense, namely, in his mind in the sense of being something he could bring before his mind, in an act of self-conscious awareness and self-ascription, in order to interrogate it with regard to veridicality or non-veridicality, truth or untruth.

So if this assumption were false, then if Descartes were asleep, the victim of an evil mind or a brain in a vat, etc., he simply could not do what he must assume himself able to do in order to succeed in the most fundamental move of the whole Meditations. This most fundamental move consists in setting up a quandary: Descartes needs to show that in order to possess beliefs and opinions with maximal rationality, he must first determine whether the items passing before his mind really are as he pre-philosophically takes them to be, namely, mostly veridical but also sometimes non-veridical perceptual experiences, mostly true, but also sometimes false beliefs and opinions. As we know, he cannot resolve this issue solely on his own; he needs to prove the existence of God qua guarantor of a positive answer to this prior question.

But if the assumption in question is false, then there is simply no room for the prior question as to whether the items passing before his mind really are as he pre-philosophically takes them to be, mostly veridical but occasionally also non-veridical perceptual experiences, mostly true, but occasionally also false beliefs and opinions. In other words, that there is this prior issue would simply be false. And if there is not in fact this prior issue, there there is no need for the move Descartes makes in order to address it, namely, proof of the existence of God as the guarantor of a positive answer to this prior issue. For if Descartes’ crucial assumption were false, then the idea that under conditions of what he calls global deception he could have anything passing through his mind in the requisite sense would be absurd. It would be as absurd as, indeed absurd in the very same sense as, supposing that under these conditions he actually was performing various physical actions, e.g., walking about in his dream or in his hallucination. In short, if he really were asleep, the victim of an evil mind, or a brain in a vat, he could not truly think that he was (although he would, of course, be hallucinating in the real world of his bed, of the computer scientist or of the supremely powerful evil mind that he was thinking). And this would mean that it were false to say that he existed as thinking (in the requisite sense) or indeed knew, even while asleep or hallucinating, that he existed as thinking.

Note to reject Descartes’ crucial assumption is not to deny that in some sense brains in a vat and the like are logically possible. Obviously, the scenario of brains in a vat is clearly logically possible. The point of rejecting this assumption is, however, not to deny this but to show that Descartes’ thought-experiment, in effect, his description and interpretation of this kind of scenario as global error and deception, is incoherent. In fact, if he were a brain in a vat or the victim of an evil mind, Descartes would be hallucinating from top to bottom: In particular, he would be hallucinating that he was wondering about various cogitationes whether they were or were not veridical or true. But there literally is no sceptical problem if even the wondering about the various items he has before his mind were no less illusory than the various physical properties and events he hallucinates himself as having or undergoing. The thought-experiment assumes, however, that at least this wondering and his existence as wondering is real and known by him to be real. This would, however, be false if one rejected Descartes’ crucial assumption.

But must one reject this assumption? That is, is it false? Here I can only sketch an answer. One way of rejecting this assumption is to be found in the work of the American analytic philosopher Donald Davidson (1917-2003). Davidson argues that, necessarily, the empirical beliefs, judgements and seemings-to-perceive Descartes notes occurring in his mind – what he calls his cogitationes – are by and large about the things which cause them. Although sometimes one can have a belief about something X which is not caused by X but by, say, the drugs one has taken, as a rule most beliefs, opinions and perceptual experiences just have to be about the things which cause them (in which case, of course, they must be mostly true or veridical).

Davidson reaches this conclusion as follows. He argues that we can make no sense of a creature’s having beliefs, opinions and perceptual experiences except as intelligible causal responses to events happening in its environment which are important to it. This means that when interpreting others and their behaviour, we have to see their beliefs, opinions and perceptual experiences as items intelligibly caused in them, given that things are thus and so. It immediately follows from this that we can only ascribe mostly true beliefs and opinions, and mostly veridical perceptual experiences, to others. Sometimes, of course, we find we have no other choice but to ascribe a false belief or non-veridical perceptual experience to another. For example, we see someone taking an umbrella from the umbrella stand as they go outside and ascribe the belief to this person that it is raining even though we know that it is not in fact raining. But this is only because we have seen the gardener spraying the window with a hose and hypothesised that the person we have seen taking the umbrella has been misled by this fact.5 In general, we ascribe false beliefs to another only alongside many true beliefs. We could not ascribe significantly many false beliefs because then we would lose all entitlement to regarding what we are attempting to interpret as a more or less rational person with beliefs and opinions at all.

If this argument is right, then we have a neat refutation of Descartes. All we have to add to the picture Davidson paints is the following claim: the beliefs, opinions and perceptual experiences we ascribe to ourselves in acts of first-person introspection are the same kinds of thing as the beliefs, opinions and perceptual experiences we ascribe to others in acts of understanding and interpreting their behaviour. Given this surely indisputable claim, it immediately follows that what we ascribe to ourselves is subject to the same principle of being mostly true as what we ascribe to others—in which case we can no more seriously regard ourselves as being massively deceived than we can others. As with the thoughts and experiences of others, so, too, with one’s own, with the thoughts and experiences one ascribes, so to speak from the inside, to oneself: these, too, are, at least as a rule, if not always, only ever about what causes them—in which case we cannot both have these thoughts and experiences in our mind, such that we could become aware of them in acts of first-personal self-ascription; and be radically or globally deceived by them. Insofar as I actually am having thoughts and experiences, insofar as I actually am identifying these thoughts and experiences as occurring in my mind (as opposed to merely dreaming or in some other way being deceived about my having and identifying them), these thoughts and experiences are as a rule, if not necessarily always, true or veridical.

Note now that this argument has a distinctive consequence: it entails that necessarily the objects of one’s beliefs and experiences occur in the same world, the same reality, as the causes of these thoughts and experiences. Necessarily, one’s empirical beliefs and judgements refer into the very same order in which their causes occur. The situation which Descartes envisages, namely, that the world in which the causes of his various thoughts and experiences occur might be quite different from the world which presents itself to him in these thoughts and experiences, simply cannot arise. So for Davidson thinking and perceiving are inherently worldly in the following sense: the world in which a subject’s ideas occur, as events occurring in its mind which it can genuinely direct its mental gaze towards, is necessarily the world which presents itself to the subject in and through these ideas.

I should note that there is another way of showing that thinking and perceiving are inherently worldly, one associated with the German phenomenological philosophers Edmund Husserl (1859-1938) and Martin Heidegger (1889-1976). I in fact prefer this way, but I cannot go into this here. Rather, let me now ask whether Descartes may in fact proceed in the way he does. For one might well ask whether it is at all legitimate that the argument of the First and Second Meditations should rely on an assumption derived from his metaphysical conception of how the human mind is in nature, which is only established in the Sixth Meditation. But we should look more closely at how Descartes proceeds: by the end of the Second Meditation, he clearly and distinctly perceives that he is as thinking but does not clearly and distinctly perceive that, as a thinking thing, he is also a material thing. And in the Sixth Meditation he argues in effect that if God exists, then He will ensure that if one thing A depends on, or is inseparably bound up with, another thing B, Descartes can clearly and distinctly perceive this to be so. But Descartes has already proved the existence of God in the Third (and Fifth) Meditation. So by the time he has reached the Sixth Meditation Descartes knows that God ensures that if something A depends on, or is inseparably bound up with, something B, then Descartes can in principle clearly and distinctly perceive this to be so. And so he may now claim clearly and distinctly to perceive that, as a thinking thing, he is not necessarily also a material thing (although he of course also clearly and distinctly perceives that he is a material thing as a matter of contingent fact). And with this conception of mind and its relation to the brain, body and nature in hand, Descartes has in effect the crucial assumption needed in order to show, via the argument from dreaming and the argument involving the evil mind, there is, prior to all questions of the veridicality or non-veridicality of his perceptual experience, the question of whether what is passing though his mind is a perceptual experience at all. It now looks like a serious issue whether he could be, even as he thinks this very thought and ponders whether this very thing before his mind is the perceptual experience it appears to be, dreaming or the victim of an evil mind—in which case he now needs to have God in the picture as the guarantor for his not in fact dreaming or being deceived by an evil mind.

These are absolutely crucial considerations. For they show that Descartes uses God’s existence not merely to solve the problem of how he can rationally claim to know through perceptual experience and through mathematical calculation. Descartes also uses it to create this problem in the first place. By the end of the Second Meditation it seems clearly and distinctly to Descartes that he necessarily exists as thinking but (he knows) that it does not seem clearly and distinctly to him that, as thinking, he must have a body. In the Third Meditation (and in the Fifth) he proves the God exists. Then, in the Sixth Meditation he proves that if God exists, then, if being F does not seem to him clearly and distinctly to be necessary for being G, then, thanks to God’s beneficence, he may rationally assert that being F is not necessary for being G. In particular, he proves that if God exists, then, if his being embodied does not seem to him clearly and distinctly to be necessary for his existence as thinking, then, thanks to God’s beneficence, he may rationally assert that his being embodied is not necessary for his existence as thinking. And so now, given that the Third Meditation has shown that God does exist, Descartes may assert not merely that he must exist at least as a thinking thing, he may also assert that he can exist at most as a thinking thing. This, however, guarantees that, as a thinking thing, he is merely contingently and in particular causally connected to a body. And this constitutes at least a necessary component of the view of mind and its relation to brain, body and world which entitles Descartes to help himself to the assumption made in the Argument from Dreaming that even in a dream (and thus, mutatis mutandis, even as a brain in a vat or victim of an evil mind) he, Descartes, still exists just as much as thinking as he does in waking life, or again, when not globally deceived either by the mad computer scientist or the evil mind.


© Carleton B. Christensen, 2008, 2010, 2011, 2012, 2013 and 2014

  1. As Clarke points out in his note on p.205, this is “(a) reference to the pineal gland, which was identified by Descartes as the likely locus of interaction between the mind and the body because, unlike other parts of the brain, which were duplicated in the right and left hemispheres it seemed as if there was only one gland like this.”

  2. Which are, according to Descartes, ultimately indivisible corpuscles – although he does not mention this aspect of his account of materiality here.

  3. By recursive application of this account of how the parts of a material body interact with one another to the parts PB and PC (insofar as they stand at a distance to one another).

  4. Descartes refers to this phenomenon on p.61 of the Sixth Meditation.

  5. Note that we are still ascribing this false belief under the assumption that the person is completely rational; this person has just made an understandable mistake.