14

Descartes, Meditations VIa

(AT VII 71-80; cf. Discourse IV, AT VI 39-40)

But now that I am starting to gain a better understanding of myself and of tha author of my being, I do not, in fact, believe that I should rashly accept all those things I appear to possess from my senses, but, at the same time, [I do not think] I should call everything into doubt.

— Meditations VI (AT VII 77-78)

The first half of Meditations VI is devoted to demonstrating two things: that bodies must exist in space outside of us, and that the mind is distinct from the body (prior to Meditations VI, it has only been argued that we know our minds better than our bodies, not that the thing in us that thinks cannot possibly be a body). The second of these points is established in the process of establishing the first.

Descartes offered three different arguments to prove that bodies must exist in space outside of us: the first is supposed to establish the possibility of the existence of an external world by appeal to what we clearly and distinctly perceive through the intellect; the second to establish its probability by appeal to what we picture in imagination, and the third to give us certainty of its existence by appeal to what is given to us through the senses. In the process of giving the second of these arguments, Descartes introduced a principle that is central to his reasons for claiming that the mind is distinct from the body, the principle that whatever can be perceived separately can exist separately. This principle is explicitly articulated and applied to establish the distinction of the mind from the body over the course of the third argument. Thus, the third argument ends up both demonstrating the existence of material things and demonstrating that thinking things are radically different from material things.

Sandwiched in between the second and third arguments is a review of what Descartes originally believed about the nature of body, of his reasons for coming to doubt these beliefs, and of what he was in a position to believe as of the close of Meditations V. It is tempting to skip over this review, both because one assumes it will merely repeat points that have already been made and because it is an irritating interruption to a chain of arguments. But the review makes many new points that become important over the second half of Meditations VI. These notes begin with a consideration of that review before passing on to the three arguments.

QUESTIONS ON THE READING

1. What sorts of material things can at least possibly exist?

2. How does imagination differ from understanding?

3. Why is imagination not part of my essence?

4. Why is it not without reason that people think that they sense bodies existing in space outside of them rather than sense only their own thoughts?

5. What sort of things are taught to us by nature?

6. What allowed Descartes to claim that the fact that I experience a pain in a certain part of my body is not enough to prove that that part exists?

7. Why should the fact that I can clearly and distinctly understand one thing without the other entail that they are really different from one another?

8. Explain the nature of the relation that Descartes supposed to hold between himself and his powers of sensing and imagining.

9. Why would God be a deceiver if my ideas of extended bodies were not caused by extended bodies?

A REVIEW

Over the first part of Meditations V, Descartes had considered what we clearly and distinctly perceive in our ideas of bodies. He had there reached the conclusion that the ideas of extension could not be materially false, but must be something positive and real. But this is not to say that extended things must exist, or that if they do they would have to be modified (cut up into numerous moving or resting parts of different shapes and sizes) in exactly the ways that are presented in our ideas. So it does not bring us very far. It is natural to ask whether some other means of obtaining knowledge might not put us in a position to say something more. Descartes accordingly proposed to take a second look at what we know about body by means of the senses, and consider what reasons we originally had for accepting those beliefs, what reasons we have for questioning those beliefs, and what we should now think given what we have learned about ourselves, God and the sciences of simple natures. Though it is billed as a “review,” this second look brings many more things to light than were identified in Meditations I, and for that reason alone it merits careful scrutiny.

a. “First of all, I will review in my mind the things I previously believed to be true, because I perceived them with my senses, along with the reasons for those beliefs.” The principal things Descartes identified as perceived by the senses are:

i. I have (or even am in totality) an extended and shaped body

ii. This body is surrounded by other extended and shaped bodies that can affect it for better or worse

iii. My sensations of pleasure and pain are indications of which bodies are affecting me for better or worse

iv. I also experience sensations of hunger, thirst, appetites of other sorts, and passions such as fear or anger. These feelings both inform me of disorders in my body and incline me what to do to relieve that disorder

v. My sensations of hardness, heat, and other tactile qualities, as well as of light, colour, smell, taste, and sound, while sensed as my own personal and immediate ideas, proceed from other bodies that differ from one another in virtue of these different sensations they cause in me

vi. External objects resemble the sensations they bring about in me

vii. There are no ideas in my intellect which did not originate from sensory experience

In recounting the reasons that led Descartes to believe these things, it is best to begin with item (v). Descartes identified three reasons for thinking that my sensations are caused by other bodies. One is that they occur independently of my will, so that I cannot make them go way in the presence of particular bodies, or make them come about in the absence of those bodies. When I hear annoying music coming from the next apartment, I cannot make it go away by an act of will. When I want to taste chocolate, I cannot bring the sensation about by an act of will. The second reason is that the ideas received from the senses have a kind of vivacity that is not possessed by those same ideas when wilfully recalled in the memory or wilfully conjured up in imagination. Remembered pain and imagined pain does not hurt the way sensed pain hurts. Both of these considerations led Descartes to conclude that his sensations did not proceed from himself. The third reason is only mentioned later, and is mentioned as one that preceded the other two. It is that we are led to think this way in advance of any reasoning by an instinct or natural impulse. We had to deal with the world as children, before we developed any sophisticated reasoning capacities. At that point, we could not stand in awe of our sensations, wondering what to do next about pains or pleasures or hunger or thirst. We needed to think that there is something outside of us that is causing pain, for example, and impulsively withdraw from that thing. Those instincts served us rather well.

Whereas item (v) has these three reasons in its favour, item (vi) has only the third. Apart from that, it is merely a counsel of ignorance. Since we receive different sensations under different circumstances, and since we have reason to think the sensations are caused by objects other than ourselves, there must be differences in the objects present in different circumstances that account for our different sensations. But we have no idea what those differences may be. In our ignorance, we adopt the plausible hypothesis that the objects are something like our sensations, and that is why they give us those sensations. But as plausible (i.e., tempting) as this hypothesis is, there is no justification for it. It is merely a stop-gap for our ignorance. What induces us to propose and accept it is really a natural impulse or instinct.

Item (vii) results from the fact that we grew up using our senses before we developed our intellectual capacities. As a consequence, most of our ideas were first obtained from the senses, and as the ideas we later form independently of the use of the senses do not have the vivacity characteristic of sensory ideas and most of them include copies of ideas originally obtained from the senses, it is easy to leap to the conclusion that all our ideas are obtained from sensory experience.

Let’s now return to items (i) and (ii). I see and touch my own body as I see and touch other bodies. So from the perspective of these senses, it would appear as just one object among others but for one thing: I see and touch all other bodies from the perspective point occupied by my body. Moreover, when objects hurt my body, the pain stays in my body when I move away from them, rather than staying in the other objects. Likewise, I cannot satisfy my hunger or thirst by feeding or watering other bodies. These experiences and others like them lead me to identify my body as one that specially belongs to me.

But I have no experiences or reasons that lead me to items (iii) and (iv). In many if not most cases I don’t know what it is about painful bodies that is doing damage to my body or what form that damage takes. I just know that it hurts and I feel natural inclination to pull away. Likewise, I can’t identify anything that connects the feeling of thirst with the impulse to drink water, and yet the feeling naturally inclines me to want to engage in that action.

To sum up, there are two main reasons for the sensory beliefs that have been itemized. The original reason is a natural impulse. But some of the beliefs have further reasons grounded in the character of our sensory experiences: their independence from our will, their special kind of vivacity, and the fact that some of them get carried around with me or my body wherever I go whereas others seem to remain behind in objects outside of my body.

b. “The I will also assess the reasons why I later called them into doubt.” Descartes’s statement of reasons for doubting sensory beliefs gives pride of place to the fact that my senses occasionally deceive me. Subsequent sense experiences show me that earlier sense experiences misrepresented the objects, or at least leave me uncertain which sensory experiences are the accurate ones. This reason is the one given first and it is discussed in most detail. The dreaming argument is mentioned only later as one of two “general considerations,” the other being that I might be constituted in such a way that I would make mistakes even in matters that I consider most true. However, this second “general consideration” has already been abandoned (Descartes mentioned in passing that it rests on considerations that he only assumed were valid). Given the way it is lumped in with an argument that has already been discredited, and only mentioned without any detailed consideration, one gets the impression that the dreaming argument has lost force in Descartes’s eyes. Of particular interest is a new consideration that makes its first appearance here. This is the “phantom limb” argument. People who have had an amputation will report feeling pain in the limb that no longer exists. This is a striking phenomenon that shows that pains may only exist in the mind, not where they appear to be, at locations in body parts. They may not, therefore, signify that there is some sort of disorder in a body part. For in this case there is no part to be disordered. Expanding on this consideration would lead us to infer that there is no sensory experience that is adequate to convince us that we have a body.

In addition for reviewing his reasons for rejecting sensory beliefs, Descartes took a second look at his reasons for accepting sensory beliefs. The principal reason, that these beliefs arise from a natural impulse or instinct, is one he rejected on the ground that nature pushes us to accept many things that reason opposes, for instance that the sun orbits around the earth. The further reason, that ideas of sense arise independently of my will and have a special vivacity, is one he rejected on the ground that there may be some other faculty in me that is responsible for producing these ideas independently of recourse to the will. We already know this from earlier meditations. We are being reminded of it because, as we will see in what follows, he meant to draw these particular sceptical considerations into question. The first is no longer as solid as it once was given that it has been demonstrated that God exists and is no deceiver. And the second falls afoul of a distinction Descartes is about to draw between what is essential to me insofar as I am a thinking being and what does not need to belong to me.

c. “Finally I will consider what I ought to believe about them now.” Descartes closed this review by alerting us to the fact that his sceptical conclusions would now need to be reassessed. There may be more to the reasons for relying on sensory beliefs than he had allowed, even if we cannot rehabilitate all of beliefs (i)-(vii) in their original form. “I do not, in fact, believe that I should rashly accept all those things I appear to possess from my senses,” he wrote, “but at the same time, [I do not think] I should call everything into doubt.”

THE POSSIBILITY PROOF FROM UNDERSTANDING

Descartes began by observing that the existence of material things or bodies is at least possible. This brief proof takes up the first half of the first paragraph of Meditations VI. Put more formally, and more plainly, Descartes’s argument looks like this:

1. God can create anything that is not impossible, absurd or contradictory (from the fact that God is all-powerful)

2. Nothing that can be clearly and distinctly perceived could be impossible, absurd or contradictory (from Meditations IV).

3. Therefore, anything that can be clearly and distinctly perceived could be created by God (from 1 and 2)

4. My ideas of bodies can be clearly and distinctly perceived, at least insofar as they contain just what is described by mathematics and geometry (i.e., extension, duration, motion and their modes) (from Meditations V)

Conclusion: It is at least possible that God could have created extended, enduring, and movable bodies (from 3 and 4).

Note that the fourth premise of this argument limits the kind of bodies that we can know God to have possibly created just to bodies that have the primary and real qualities of size, shape, position, motion, and so on. Sensible qualities like colour and solidity are not mentioned. This is a consequence of the possible material falsity of our ideas of these qualities, discussed in Meditations III. If we are going to make claims about what God might possibly have created, we have to be sure that what we have in mind really is something, and not nothing. But insofar as it is an open question whether sensible qualities are ideas of real, positive things or confused perceptions of nothing at all, it remains an open question whether there would be anything for God to create answering to our ideas of sensible qualities. Perhaps God just created minds that confusedly perceive nothing as if it were sensible qualities (or, alternatively, perhaps God just created minds that confusedly perceive the more primary and real qualities of extension and its modes as if they were sensible qualities).

Of course, it might also have been the case that God just created minds that have ideas of the primary and real qualities, without actually making objects that in any way resemble those qualities. But it is at least possible that God might have created something corresponding to these ideas as well, whereas we cannot affirm this concerning sensible qualities.

THE PROBABILITY PROOF FROM IMAGINATION

The second proof is somewhat stronger and establishes a probability rather than a mere possibility of the existence of bodies.

The proof proceeds by remarking on the strange fact that we have such a thing as an imagination at all. The imagination merely serves to allow us to vividly picture some (but not all) of the things we can quite well conceive with our intellects. In other words, it is a redundant function. This sudden talk of a separate faculty of imagination may seem bewildering in light of Descartes’s claim, in Meditations II, that there is only one cognitive faculty, the understanding, which images and senses as well as understands. But even though Descartes rejected the existence of three distinct faculties, he did think that the understanding grasps two distinctly different kinds of ideas. Some ideas are literally like images or pictures. They seem, as it were, to take up space and to consist of spatially arrayed parts. Others are more like definitions or lists of essential features that a thing must exhibit. They seem to be merely formulae in accord with the things we can picture are made. Thus, imaging or picturing a triangle is one thing, and grasping the concept of a triangle or understanding what it means for something to be a triangle is something else. Though both the image and the judgment are thoughts grasped by the understanding, Descartes often said that when the understanding has thoughts of the former kind it has a special kind of thought and should be said to be imaging or sensing, whereas when it has thoughts of the latter kind it understands in a more proper and narrower sense (see, for instance, AT VII 78).

Descartes illustrated this point with examples of geometrical features. Triangles and pentagons may be imagined as well as understood; that is, we can image or picture them, as well as simply grasp the definition or list the conditions that have to be satisfied for something to be a triangle or pentagon. We are aware by introspection that these two acts, getting an idea that is a literal image or picture in the mind’s eye and judging about the content, are very different acts and involve, as Descartes put it, different “efforts” on the part of the mind.

We are also aware that imagination is redundant — that everything that can be imagined can be understood, but not everything that can be understood can be imagined. A hundred- or thousand-sided figure, though it may be very clearly and distinctly understood in all its aspects, cannot be brought to an image — at least not any image adequate for us to distinguish that figure from a 99- or 999-sided figure, or indeed from a circle. (Any image of such a figure would have to be “confused” in the technical sense of the term, though the idea had of the same figure by the intellect would be “distinct.”)

Our imaginations therefore seem to be a kind of annex to our cognitive powers. We would still be able to think the same things if we lacked them. This led Descartes to claim that our imaginations are separable from us. They must be separable because we would still exist as the same sorts of being with all the same abilities if we were to lose them. So they cannot be part of our essence, that is, part of what makes us what we are. They would seem to reside in something distinct from us, to which we are merely contingently attached.

There is an important principle that is tacitly invoked here, the principle that if one thing is conceivable apart from another (for example, if I as thinking being am conceivable apart from any capacity to imagine), then those two things must be at least logically separate. Even if in fact they are always encountered together in experience, the one could in principle exist without the other. This is what, in the literature, is called the separability principle:

Separability principle: Whatever things can be conceived separately from one another must be really distinct, and separable in principle from one another.

The separability principle is the inverse of the principle concerning clear and distinct perception operative in Meditations IV, where it was claimed that if we clearly and distinctly perceive one idea, and find another contained in it, then we must judge the two are related. Here, if we clearly and distinctly perceive one idea, and do not find the other related to it, then we can judge that the two have nothing to do with one another, so that God could create the one apart from one another. Even if they in fact always occur together in our experience, their conjunction is merely accidental or coincidental.

Some examples might help to illustrate this claim. I can think of an apple without having to think of redness. The apple is in this sense separable from redness and could at least in principle exist apart from it, even though in fact a lot of apples might be red. Or, I can think of a city without thinking of it as having a police force. There might be no city without police but it is at least conceivable that there might be one, and so it seems at least possible that such a place might exist. But I cannot conceive of an apple without conceiving of a fruit, or a city that has fewer than two buildings. These latter things cannot be conceived separately from one another and Descartes took this as an indication that they might well not be able to exist separately. But be that as it may, we can be sure that if one thing can be conceived without having to think of another, then it must be essentially distinct from the other (in the sense that the form or essence that makes that thing what it is involves nothing that goes into the form or essence that makes the other thing what it is), and so could exist apart from it.

Descartes used this principle to powerful effect in what follows.

To return to the main argument, having speculated that our imagistic ideas could well depend on something distinct from us, to which we are merely contingently attached, Descartes went on to ask what such a thing might be. The most characteristic feature of our ideas of imagination is that they are pictures of things. They seem to take up space and to consist of spatially arranged parts. Accordingly, he speculated that perhaps there is something attached to us that is actually extended in space, like a little theatre screen or a canvas on which pictures can be projected or painted. The intellect could then get two different kinds of ideas, one that it receives when it turns to contemplate this canvas or screen and the other when it merely judges about the ideas it finds within itself. In the former case, the pictures on the stage or screen would be the objects that the ideas in the intellect are about (they would supply the objective reality for our ideas of imagination). However, it is important to stress that they would not be those very ideas. The mind’s ideas, whether they are imagistic ideas of imagination or sense, or whether they are judgments of the understanding, exist only in the mind, which cannot be affirmed to be extended (and will soon be proven to be unextended). The pictures on the extended, physical organ that we might call the corporeal imagination are at best causes of a particular kind of imagistic idea being created in the mind. The intellect would experience these imagistic ideas in a very different way. Rather than “judge” them as something it finds within itself, it would “envisage” them as if they were present before it, and this would account for the peculiar vivacity of imagined ideas as well as for our sense that they are very different from the other ideas formed by the intellect and in a sense the result the operation of a distinct knowing power.

This theory may seem too speculative, and Descartes himself did not presume to claim that we can know for sure that this is what causes the intellect to have imagistic ideas. But he did think the theory is highly probable. The theory is in fact just the theory of the operation of the imagination described by Aristotle in De Anima III and accepted as dogma by theorists of perception and knowledge for centuries. According to that theory, there is actually a bodily organ, just like the eyes or ears, but located inside the body somewhere, probably in the brain, that receives imprints or images from external objects. The intellect was supposed to form many or even all of its ideas by “contemplating” the images impressed by the external sense organs on the soft matter of this internal organ and then subsequently abstracting the universal “form” from the particular way in which the matter of the sense organ is impressed. The main difference between Descartes’s version of the theory and Aristotle’s is that Aristotle took the physical organ in the body to itself be the imagination and imagining to just consist in the imprinting of this organ. Descartes, in contrast, takes imagining to be a special act of the mind or intellect, involving getting a unique kind of idea through somehow turning to and contemplating the organ. And, of course, Descartes did not accept that the intellect must get all of its ideas by contemplating images impressed by the senses on the imagination. This supposition would contradict his position on the innate idea of God, and a little further on in Meditations VI, he explicitly condemned it.

To return to the argument, if Descartes’s account of the operation of imagination were correct, it would imply that at least one extended body must exist, namely the part of our brains that we contemplate when we get ideas of imagination. This is why Descartes said that a consideration of the nature of our imagination establishes at least a probability that bodies might exist.

However, Descartes had to admit that the proof does not establish a certainty of the existence of a corporeal imaging organ. Perhaps other explanations could be found for the difference between ideas of imagination and those of understanding that would not need to invoke these same presuppositions.

THE ACTUALITY PROOF FROM THE NATURAL IMPULSE OF THE SENSES

Descartes final and most decisive proof for the existence of bodies takes off from the natural impulses he had found to be the original reasons for our sensory beliefs. These impulses now need to be understood in the light of what Descartes has learned about the goodness of God and about what is separable from and what is proper to his nature, when he is considered as a thinking being.

In the process of giving this final proof, Descartes uncovered an argument for concluding that the mind must be a radically distinct kind of thing from the body. This discovery helps his proof for the existence of bodies along. It also helps to demonstrate that his mechanistic philosophy does not reduce everything to matter and can provide for the existence of an immortal soul.

The proof for the real distinction of the soul from the body. The argument Descartes proceeded to give for the “real distinction” of the soul from the body appeals to the separability principle introduced earlier. He pointed out that I am able to know that I must exist, but despite this fact am still able to doubt that I have a body. In other words, I can conceive of myself very clearly and distinctly as a being that senses, imagines, thinks, wills, desires, affirms, doubts, denies, and feels, and cannot doubt that I exist and do any of these things when I experience myself doing them — but I can doubt that I have eyes, hands, brain, or any sort of physical body. The dreaming argument already sufficed to establish that.

But, Descartes continued, if one thing (for example, the thinking part of a person) may be very clearly and distinctly conceived without having to include another thing (namely, extension) in the conception, then those two things must be essentially distinct. The one (thinking and its modes) must have nothing to do with the other (extension and its modes), so that were the one separated from the other (extension removed from the thinking thing), it could continue to exist on its own. If this were not the case — if separating the thinking part from the extended part were to destroy the thing, then we should not be able to distinctly perceive the thinking part without realizing that some idea of extension must be included in it as part of its essence. A distinct perception of an idea, as noted earlier in connection with Meditations V, is one that contains separate ideas of all the parts of that idea. Any necessary connections between two things would have to be revealed by such a perception. So being able to clearly and distinctly conceive of thought and all of its modes (sensing, imagining, believing, doubting, conceiving, willing, desiring, feeling, etc.) while still being able to doubt whether the thinking being is extended, proves that the latter really may be separated from the former.

By similar argument, since we can conceive of extension and its modes (size, shape, position, motion, order) without having to conceive of any of the modes of thought, body must be similarly distinct from mind and capable of existing apart from it.

This does not rule out the possibility that I might still be joined to a body. The point of Descartes’s argument is just that I am in principle separable from any bodies that I may be joined to. Descartes wanted to go on to claim that I do in fact have a body, but he insisted that I am not so intimately united to my body that I could not be removed from it without being destroyed. What I really am is just the thinking part, which is a sort of detachable module that can, at the will of God, either be connected to a body or removed from it without its own integrity being in any way undermined.

The proof for the existence of bodies. Descartes’s final proof for the existence of material things appeals to the fact that I do not just understand the properties of extension or have imagistic ideas of bodies, but also have sensory ideas of bodies. Like my ideas of imagination, my ideas of sensation are pictorial in nature and involve “envisaging” bodies “as if they were present.” But unlike my ideas of imagination they do not occur consequent upon an effort of my will. Instead, when I form them, I experience myself as something passive that is being affected by something else. For, rather than require any effort on my part, the formation of these ideas happens without my wanting it and frequently even contrary to my wishes. I can both fail to get ideas of sense when I want to have them, and have them when I do not want them. This gives me a “natural impulse” to consider these ideas to have been created by something else.

Of course, just because I have no control over my ideas of sense, it does not follow that I do not cause them, and just because I have a natural impulse to suppose they have some external cause, it does not follow that I myself do not cause them, or that they could not be caused by some other being that, like myself, could serve as an “eminent” cause of ideas of extension. All that follows is that whatever it might be that causes these ideas is something that operates independently of my will. Moreover, natural impulses are not the same things as clear and distinct perceptions. When I have a clear and distinct perception, it compels my will to assent. But natural impulses can be resisted. And some of them are contrary to what I clearly and distinctly perceive, which proves that they are not to be trusted. These are the points Descartes had made at the close of his review, at AT VII 77.

But these concerns don’t sit well with what has since been established about my own nature and about God’s nature. Suppose there were some hidden faculty in me that produces my ideas of sensible qualities independently of my will. Then simply for the reason that this faculty is hidden and that ideas do not seem to come from anything in me, it follows that I can clearly and distinctly perceive myself without having to include the thought of any such faculty as being a part of me. This means that, even if I do have such a faculty, it would be an unnecessary add-on to my being. God would not have needed to create me with it. But then why would God have created me with such a faculty?

Things get worse when we consider that I also have a natural impulse to believe that my sensory ideas of bodies come from things that exist apart from me. Even granting that there are some natural impulses that are contrary to what I clearly and distinctly perceive, this particular natural impulse is not among them. I may have doubts and wonder whether bodies exist outside me or not. But I do not clearly and distinctly perceive that it is impossible that there should be bodies existing outside of me. On the contrary, I clearly and distinctly perceive that it is entirely possible that there may be such things, at least insofar as they are considered to be forms of extension. Descartes recognized that God might have reasons for allowing me to fall into error. But he insisted that the goodness of God would not permit him to allow me to fall into error unless I were given ways of discovering and correcting my mistake. But if it is wrong to believe that there are external objects, I would seem to have no way of discovering the error of that belief. If God gave me a strong natural impulse to believe that my sensory ideas come from external objects when there are no such objects, and when all those ideas are eminently caused by himself or some other spirit or, worse, some hidden faculty in myself, and if God could very well have created me without that impulse and without that hidden faculty without diminishing me in the least, then it is hard not to conclude that God must be a deceiver. Since God is no deceiver, we seem compelled to accept that external objects must exist.

This is a complex argument, so let’s run through it a second time from a different angle. Why, Descartes asked, would an all-good God have put something into me that causes particularly vivid ideas of sensation independently of my will, and so triggers an instinctive impulse to think that these ideas do not come from me but from other things outside of me? We cannot think that God had to do this. For, Descartes claimed, I clearly and distinctly understand that it is possible for a thing to think without also having to sense. Accordingly, the separability principle dictates that it ought to have been possible for God to have created me without a capacity to produce ideas of sensation, had he wished to do so. Nor can I think that his doing so would necessarily have made me any worse off. Were there nothing outside of me that corresponds to my ideas of sensation and were all my ideas of sensation merely caused by something in me that invents these ideas independently of my will, then I would not be diminished in the least were I to lack this capacity and not get any ideas of sensation. After all, everything that I can sense, I can just as well understand. Were my sensory capacity to serve no other purpose than to invent fictional ideas that teach me nothing that I could not just as well learn from unassisted understanding, it would be superfluous. Indeed, it would be worse than superfluous, since insofar as it makes my ideas occur independently of my will it tempts me to suppose that the ideas are caused by something outside of me. Admittedly, after what I have learned from Meditations IV, I can resist the temptation to make this hasty judgment. But I cannot deny that I feel a strong natural impulse to make it anyway, and that before I was instructed by Meditations IV I even gave in to it. But that impulse is just as unnecessary as the sensory capacity. I did not need to be created with it. And given that I was created with it, I have no way of discovering the error of what it tells me. Even though I may not clearly and distinctly perceive the truth of what it tells me, I also do not clearly and distinctly perceive that what it tells me is in error, and that there are no external objects. If I need not have been created with a mental capacity, and if the use of that capacity serves no other purpose than to deceive me, or to tempt me to into deception, then an all-good God would not have given it to me. If I have ideas of sensation and a strong natural impulse to think that I am not there cause, this cannot be because I myself am producing them unknown to myself. An all-good God would simply not have made me that way. So something else must be producing my ideas of sensation.

What would such a thing be? According to what Descartes had already established in Meditations III, it would have to be something that “formally” or “eminently” contains at least as much as is represented in my ideas of sensation. This means that it would either have to be something that itself literally (i.e., “formally”) contains all the reality I find in my ideas of sensation, or else something that is able to “eminently” cause all this reality. Recall that Descartes considered our ideas of sensation to consist of shaped and sized pieces of extension that have sensible qualities like colour, solidity, and heat attributed to them (Meditations III). Recall further that he maintained that sensible qualities might not be “real,” but might be materially false ideas that we ourselves cook up when our senses are not affected by anything real (Meditations III). However, extension and its modes (shape, size, number, and motion) definitely are something real with a nature independent of us, as is proven by the fact that we cannot legislate the content of the principles of geometry and arithmetic (Meditations V). Recall finally that Descartes maintained that even if, as we have just learned, we ourselves could not be the cause of our ideas of extension, other unextended spirits, such as angels, demon deceivers or God might nonetheless still be eminent causes of these ideas (Meditations III). So at this point it looks as though the cause of our ideas of sensation would either have to be bodies that are themselves actually extended (though not necessarily possessed of any sensible qualities) or else unextended spirits with special powers to “eminently” create ideas of extension in us.

At this point Descartes appealed to our natural inclination to suppose that our ideas of sensation are caused by objects that are at least something like the objects those ideas depict. Were this propensity wrong, I do not see how I could ever discover my error. The fact that sensible qualities occur in opposed pairs might alert me to the possibility that one or both members of each pair might be a “materially false” idea of nothing, but I can find no evidence that suggests that my ideas of extension proceed from nothing. Consequently, Descartes maintained, were the cause of my ideas of sensible things not extended, God would be a deceiver, either for giving me ideas of sense that do not refer to anything that actually exists when I could perfectly well exist without those ideas, or for giving me an incorrigible propensity to believe that my ideas of sense proceed from extended things when they are in fact caused by other spirits. Since God is no deceiver, we can infer that neither of these things is the case. Our ideas of sensation are not caused either by God himself or by other spirits. It remains that they are caused by objects that are literally extended.

This argument has proceeded at some length, but its main points may be quite briefly summarized.

1. I have an incorrigible natural inclination to suppose that my ideas of sensation are not caused by me, and an incorrigible natural inclination to suppose that they are caused by something that formally (i.e. actually) contains at least as much as I clearly and distinctly perceive to be a real feature of those ideas.

2. God did not have to give me either of these inclinations.

3. Therefore, God would be a deceiver were my ideas of sensation not caused by something outside of me that formally contains at least as much as I clearly and distinctly perceive to be a real feature of those ideas.

4. God is no deceiver.

5. Therefore, the cause of my ideas of sensation must formally contain at least as much as I clearly and distinctly perceive to be a real feature of those ideas.

6. I clearly and distinctly perceive extension to be a real feature of my ideas of sensation.

7. Therefore, extended objects (i.e. material things) must exist.

Note that this argument only allows us to infer that the bodies that cause our ideas of bodies must formally contain all the reality that is represented in our ideas of bodies. This allows us to infer that the cause of our ideas of bodies must be something that is extended, since extension is represented in our ideas of bodies, and, as Meditations V has shown, our ideas of extension contain something true and real. However we cannot legitimately infer that the cause of our ideas must be extended in exactly the same way that our ideas are extended. Just as any geometrical shape could be thought to be contained on a blank piece of paper, so any extended thing could be the “blank space” that serves as the formal cause of any shape whatsoever. Moreover, the argument does not allow us to infer that the cause of our ideas of extension must have any sensible qualities. For, as the discussion of material falsity in Meditations III demonstrates, questions can be raised about whether the sensible qualities that are contained in our ideas of bodies refer to anything true or real, and the argument only allows us to infer that the cause must formally contain all the reality that is represented in our ideas.

Of course, this is not to deny that bodies might on occasion be extended in just the ways they are represented as being in our ideas, or even that bodies may have colours and other sensible qualities. Descartes’s point was just that the argument is not strong enough to allow us to draw these further conclusions.

ESSAY QUESTIONS AND RESEARCH PROJECTS

1. Is Descartes entitled to affirm the separability principle? That is, from the fact that I can clearly and distinctly perceive one thing without another, does it have to follow that the one thing must be capable of existing apart from one another?

2. Has Descartes made a convincing case for the claim that minds could exist apart from bodies and that thought and feeling do not have to involve any operation of an extended thing?

3. According to Descartes, I can be sure that external objects exist because I find in myself a strong inclination to suppose that my ideas of sense are caused by such objects, and God would be a deceiver for giving me such an inclination were there no such objects in existence. But, by the same token, I find in myself a strong inclination to suppose that bodies possess colour and other sensible qualities. Yet Descartes appears not to have wanted to conclude that external objects must therefore be coloured and possessed of the other sensible qualities. How can this be? Is Descartes’s position on the demonstrability of the existence of extended objects but the undemonstrability of the existence of coloured objects consistent? If so, say why. If not, say why not.