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Descartes, Meditations V

(cf., Discourse IV, AT VI 36-39)

when I first discover them, it seems I am not so much learning something new as discovering something I knew beforehand.

– Descartes, Meditations V

Having eliminated the demon deceiver argument and his doubts about demonstrative sciences that just examine ideas and make no existence claims, Descartes’s next job was to reassess the dreaming argument and his doubts about the existence of other things outside of himself, particularly including the bodies revealed by his senses. But before addressing this question, Descartes declared that it might be wise to first consider his ideas of sensible bodies, and identify what is clearly and distinctly perceived in those ideas.

Descartes proceeded to focus on the positive rather than the negative: on what is clearly and distinctly perceived in these ideas rather than on what is not. But all the same it is worth recalling something that was already established in Meditations III. We should not expect that Descartes would include sensible qualities like color or heat among those things that are clearly and distinctly perceived in our ideas of bodies. The sensible qualities are so far from being clear and distinct that they are not even clear. They are so obscurely perceived that we can’t even tell them apart from what they are not. This is because we can’t tell whether they are ideas of real, positive things, or instead “materially false” ideas of the absence of what is real and positive. They do not figure on Descartes’s list of what is clearly and distinctly perceived in our ideas of bodies.

In contrast, extension and its “modes” or modifications (shape, size, orientation, motion, number) are not only clearly but also distinctly perceived. In addition to having an idea of extension, we have ideas of its “parts,” that is, of all the different ways in which it can be cut into shapes of various sizes, and of the way these bits can be turned and moved and arranged. Moreover, even though we may doubt the existence of an external world, containing anything that is extended, and consider all our ideas of shapes to be nothing more than images in our minds, these images have their own natures over which we have no control. For example, try as we might, we cannot form an idea of more than four equidistant points. There is something about the nature of extension itself that independently forbids us from doing this. Similarly, we cannot form ideas of cubes with more or less than six faces, or of triangles with internal angles that are not equal to two right angles or largest angles that are not opposite their longest sides. Again there is something about the nature of extension that, independently of us, forces our thoughts about shapes to conform to particular laws, which we call the laws of geometry. This compels us to recognize extension as something that has a “reality” of its own and that certainly is not materially false (nothing could not constrain our thoughts to take on a certain form), even if extended objects may not exist outside of us.

It turns out, therefore, that what we really know about sensible things is not what we originally thought. What we really know is just that they are extended, and that their extension is susceptible of being modified in accord with the laws of geometry and mathematics. We do not know that they are coloured or hot, or even that they are solid or heavy. That having been said, it still remains a question of whether anything exists outside of us that corresponds to these ideas.

In addition to rehabilitating some of what we thought we knew about sensible bodies, Meditations V presents a further proof for the existence of God. Unlike the a posteriori and demonstrative proof of Meditations III, which starts from the fact that an idea of God exists in me and asks what might cause this idea, this proof is an a priori proof, like the proofs given in mathematics, which rests on an analysis of what is contained in the idea of God. Descartes seems to have wanted to make the point that the existence of God can be demonstrated in the same way, and with the same degree of evidence, as any proposition of mathematics. This would answer those atheists who doubted the existence of God but still considered mathematical propositions to be beyond doubt. But he also went on to claim that knowledge of the existence of God is more fundamental than any truth of mathematics. This is because a prior proof of the existence of God is what eliminates the demon deceiver objection, enabling us to be certain of what we clearly and distinctly perceive not only at the time when we clearly and distinctly perceive it, but also later, when we only remember having clearly and distinctly perceived it. Not only would an all-perfect God not want to deceive me, he would not allow any other very powerful being to do so, and he would ensure that in any cases where I am deceived I am supplied with some way of discovering my error. Were my memory so unreliable that even frequent review of the same demonstration could leave me systematically deceived, there would be no hope of discovering errors. We would have to go back to clearly and distinctly perceive the matter all over again, and then we would be able to make no progress beyond that point, to think about anything else. Memory must therefore not be so unreliable that, even in those cases where we remember having repeatedly attended to the matter and clearly and distinctly perceived the same result, we are misremembering. It is assurance of the existence of God that establishes this, and so makes demonstration in the mathematical sciences possible.

QUESTIONS ON THE READING

1. Which ideas of things are distinct?

2. How is it that Descartes could say that my ideas of geometrical shapes are not made by me, even though I can imagine them on my own, and call them up or make them go away at will?

1. How did Descartes respond to the objection that I may have learned of geometrical shapes from sensory experience of similarly shaped objects, and that the reason why I seem to “remember” these shapes rather than to have produced them myself in my own imagination is that I am really just remembering something I have seen before?

2. Why, according to Descartes, can existence not be separated from the “essence” (i.e., the definition) of God?

3. How did Descartes respond to the objection that I might arbitrarily attach the idea of existence to the idea of God in my imagination, so that from the fact that I choose to make this connection, it in no way follows that the connection must be true and that God must exist?

4. How did Descartes respond to the objection that just because I cannot imagine God without attributing existence to him, it does not follow that God must exist because my thought imposes no necessity on things?

5. Supposing that the existence of God is not yet certain, under what circumstances would it be possible to doubt what one has clearly and distinctly perceived?

6. How is it that all demonstrations in mathematics might be said to rest on a prior demonstration of the existence of God?

NOTES ON THE READING

a. The reality of our ideas of extension and its modes. Descartes opened Meditations V by turning to the internal world of his ideas and asking which of them could be considered to be ideas of things that are “real” or positive. In asking this question he was not asking which of our ideas are of things that actually exist. For Descartes, the concepts of reality and actual existence are importantly distinct. Reality has to do with how things are described, that is, with the sorts of characteristics or qualities that are ascribed to things. Actuality has to do with whether things exist. Descartes shared the traditional notion that the qualities that are ascribed to things come in opposed pairs (e.g., bright and dark, hot and cold, light and heavy, moist and dry). One member of each pair is positive or real and the other is privative. Positive qualities are something whereas privative qualities are actually nothing — they arise from the absence of their positive counterparts. Consequently, things can be more or less “real” depending on how many positive qualities they have. Reality, in this sense, has nothing to do with existence. Things that do not exist, like dragons or unicorns, can nonetheless have positive qualities (e.g., extension and motion). Things that do exist, like ice or earth, have privative qualities (e.g., coldness and darkness). There can be less “reality” (fewer positive qualities) possessed by some things that do exist than by other things that do not exist.

Note that as far as our ideas are concerned, existence is not in question. Just as I cannot doubt that I exist, so I cannot doubt that my ideas exist. Indeed, the two are one and the same, since for me to be aware of my existence just is for me to be aware of the thoughts or ideas that are within me.

However, we have already seen in Meditations III that the reality of our ideas is in question. Our ideas of sensible qualities are so obscure that we cannot tell for sure whether they are materially false ideas of privations or real ideas of positive qualities.

Descartes’s first job in Meditations V was to prove that at least some of our ideas are unquestionably of real or positive things. These are our ideas of the extension of things and of the ways this extension can be modified. The idea of extension is the idea of a quantity rather than a quality of things. Specifically, it is the idea of being continuously spread out over three dimensions and being divisible into differently located parts with different sizes and shapes and states of motion or rest. (Number, location, size, shape, and motion are ways in which parts of extension are modified, or “modes” of extension.) Moreover, the shapes are clearly and distinctly perceived to have certain natures. Triangular shapes, for instance, must have internal angles equal to two right angles. Right angle triangles must have their hypotenuse equal in length to the square root of the sum of the squares of their sides. There are many propositions like this — all the propositions of geometry. These propositions are known simply by perceiving what is contained in our ideas of different shapes.

Descartes made an odd remark concerning these judgments. He said that when I first discover them it seems I am not so much learning something new as recalling something I knew beforehand. The claim is reminiscent of Plato’s assertion (e.g. in the Meno) that mathematical truths are recollected from an experience had before birth when the soul, freed from the body, was able to perceive ideal geometrical shapes with the eyes of the mind alone. But despite a degree of affinity between Plato’s views and Descartes’s, Descartes likely had a different point in mind. When I remember something there is a sense in which it is up to me: I can choose which of my memories to remember and when to remember it. But there is also a sense in which remembering is not up to me: I cannot change the content of my memories, but can only remember things that actually happened to me in the past. Other things can be imagined, but not remembered. Descartes’s point was similar, though not identical. While I can imagine ideas of this or that geometrical shape at will, and make them come or go, or exchange them for others, any particular shape I choose to imagine is imagined under constraints that are beyond my control, much as the content of my memories is beyond my control. There are properties of geometrical shapes that I cannot alter. A triangle must have its longest side opposite its largest angle, and must have internal angles that are equal to two right angles. A cube must have six faces. Given four equidistant points, there cannot be anywhere where a fifth point could be placed that is equidistant from each of the other four. Some of these features may be features that I have never used my understanding to clearly and distinctly perceive, but when I do once perceive them, even for the first time, I do not have the feeling that I have put them into the triangle, but instead think that the feature was present, unnoticed, in all the triangles I thought of in the past. This is another sense in which I seem to be “remembering” rather than perceiving these features.

Of course, this raises a question: might I really be remembering? That is, might I originally have obtained my ideas of extension and shapes by sensing extended and shaped objects, so that the reason why these ideas appear a certain way to me now is just that I am remembering them as they originally were? Descartes rejected this possibility on the ground that we are able to imagine geometrical shapes we are sure we have never seen before, but these shapes, too, have certain essential features that we cannot alter.

These reflections led Descartes to conclude that, despite the fact that there may be no extended things existing outside of us, our ideas of these things have a real and unchangeable nature that is independent of us. While I can make my ideas of triangles come and go, I cannot make an idea of a right angle triangle with a hypotenuse that is greater or lesser in length than the square root of the sum of the squares of the lengths of its sides. This feature of triangles is not up to me to determine and beyond my control to alter. Consequently, the Pythagorean theorem, which expresses this feature, states something real and true and not merely something fanciful. And the same may be said of all the other propositions of geometry and arithmetic. But nothingness or a privation of reality cannot constrain my thought to take on a certain form. Only something real can do that. Thus, our ideas of extension and its modes must be ideas of something that is positive and real. They cannot be materially false ideas of nothing or of a privation of reality.

Again, this is not to say that extended things must exist. Though the ideas of extension are of a quality that is positive and real, it remains a question whether there is anything that possesses this positive quality. We can, however, affirm that whatever we learn through geometry about extension has the status of a general rule that would have to be obeyed by extended objects if they were to exist. However, it is only in Meditations VI that considerations are brought forward to establish that extended things are more than merely possible in conformity with these general rules.

b. The ontological argument for the existence of God. At this point, Descartes paused to observe that there is one case where inspection of the content of ideas can establish the actual existence of an object corresponding to that idea. This is the case of the idea of God. Our idea of God is the idea of a supremely perfect being. But, according to Descartes, existence adds to the perfection of a thing. This is proven by the fact that, if you were offered a choice between having ten actually existing dollars and ten imaginary dollars, you would choose the actually existing ones. Your preference for the actually existing ones proves that existence adds to the perfection of a thing. Consequently, were God to lack existence, God would be less than supremely perfect, which is contrary to what the idea of God tells us. We must conclude, therefore, that our idea of God is the idea of an existing thing. Existence is as inseparable from God as having internal angles equal to two right angles is from a triangle, and is demonstrable in the same way: by clearly and distinctly perceiving what is contained in the idea of the thing. Were God not to exist, our idea of God would be false (since it represents God as existing), and we know that nothing that we clearly and distinctly perceive could turn out to be false.

(For that it is worth, the example of the ten dollars is actually due to Immanuel Kant, who spoke of thalers (“tolers”), a silver coin in use at the time from which the name “dollar” is derived. Kant, who was no supporter of Descartes’s argument, used the example to express an anti-Cartesian point: that ten real dollars do not contain one penny more than ten imaginary dollars, and so are not any more perfect.)

Descartes proceeded to raise and answer three objections to this argument. The first is that, as he put it, questions concerning the existence of a thing are distinct from questions concerning its “essence” or definition. We can define an idea as we will — or as we clearly and distinctly perceive it to be — but it still remains a question whether anything exists that corresponds to the idea as thus defined. When defining a thing we list the real features or qualities that it has to possess in order to be that sort of thing. But many philosophers have maintained that existence is not a real feature or quality. Saying that something exists does not add to the reality of the thing being defined or make it a different kind of thing, as if an existing dragon were a different species of animal from a non-existing dragon, the way a rational animal is a different species from an irrational animal. When we say that something exists we are merely adding the information that there is an object in the world that corresponds to the idea; we are not listing any real quality of the idea itself. As Kant later to put it, ten existing dollars does not contain one penny more than ten possible dollars. If we prefer the one to the other, it is not because the one is greater or more perfect in any way, but only because we know that the one has a partner in the external world as well as being a mere idea in the mind.

Descartes’s response to this objection was to dig in his heels and insist that existence nonetheless adds to the perfection of a thing. We only think it does not because in most (and perhaps all) other cases existence is not part of the essence of the thing. This has made us accustomed to think that existence is not a perfection. But we discover the error of this customary impulse when we consider the idea of an all perfect being, since in that case a clear and distinct perception on the part of the understanding compels the will to assert that a supremely perfect being would be less than perfect were it not to exist.

A second objection is that our thoughts impose no necessity on things. So simply because we conceive of a certain idea, it does not follow that anything must exist corresponding to that idea. As one of the objectors to an earlier version of Descartes’s argument put it, I can conceive of a supremely perfect island. But it does not follow that any island has to exist.

Descartes’s response to this objection was to admit that our thought imposes no necessity on things, and that simply because we do conceive of something as being a certain way, it does not follow that anything must exist that actually is that way. But, he proceeded to observe, in the case of the idea of a supremely perfect being I must conceive of existence as one of the attributes of the being. This is not something that is up to my choice, just is it is not up to my choice to conceive of a triangle that has internal angles that sum to anything other than two right angles. In both of these cases, far from it being the case that my thought imposes a necessity on things, the nature of the things imposes a necessity on my thought, which compels my idea to take on a certain form.

A further problem with the counterexample of the supremely perfect island is that conception is not just arbitrarily concocted but even self-contradictory. To be an island is to be surrounded by water, which means being only finitely extended. That already means being less than supremely perfect. An island is also just a clump of earth, lacking powers of vegetation, growth, nutrition, reproduction, self-movement, sensation, reasoning, memory, etc. So there are a great many ways in which an island is imperfect. That makes the idea of a supremely perfect island maximally confused — self-contradictory. If we modify the example by adding perfections to the idea of the island, it stops being an idea of an island and becomes the idea of God. It is only when we consider the idea of a being that is supremely perfect (and there can only be one such being) that we find a reason to assert existence. In all other cases, where the thing we conceive is thought to lack some perfection or other, a further reason would have to be given why that being should not also lack the perfection of existence.

A final objection is that the idea of a supremely perfect being might be like the idea of a supremely perfect island — it might be an obscure or incoherent idea to which nothing can correspond. Existence only follows from the idea of God because we have verbally included something in the idea (supreme perfection) that necessarily entails existence. But we need not and perhaps ought not to have defined the idea that way. Similarly, were we to define a four sided figure as a figure that can be inscribed in a circle, it would necessarily follow from the definition that a rhombus must be a figure that can be inscribed in a circle. But that is wrong, which goes to show that the idea was obscure and incorrectly formed.

Descartes’s response to this objection was to remark that when I form an obscure or incoherent idea, I am not constrained to form the idea in any particular way. But while it is up to me to think of a supremely perfect being or not, when I do think of this idea, I am constrained to conceive of it as an idea of something that exists. Similarly, while it is up to me to think of a triangle or not, when I do think of this idea, I am constrained to conceive of it as an idea of something that has internal angles equal to two right angles. In the case of the four sided figures, I am so far from being constrained to conceive them as all being such that they can be inscribed in a circle that I am on the contrary easily able to conceive counterexamples to that claim, and so clearly and distinctly conceive that it must be false.

It seems strange that Descartes should have suddenly detoured to offer yet another argument, his third, for the existence of God. One consideration that may have motivated him to return to this topic is that his proofs of God’s existence in Meditations III are proofs of a quite different sort from the one he offered here. The Meditations III proofs are what can be called a posteriori proofs or proofs “after the fact.” In an a posteriori proof, the conclusion is established only after the fact of the existence of some other thing has first been established. Thus, in Meditations III, Descartes first needed to establish the existence of the idea of God, or the existence of himself as a thinking thing that has an idea of God, before he could prove that God must exist. The Meditations V proof, in contrast, like all the proofs in geometry, is an a priori proof or a proof “in advance of the facts.” In an a priori proof one does not first need to establish that anything else exists. One proceeds merely by analyzing or defining or, as Descartes would have preferred to put it, clearly and distinctly perceiving what is contained in the idea of a thing, and the analysis alone reveals the truth one is seeking. This is of course the method of proof that Meditations IV recommends as the way to uncover the truth, and Descartes may have been concerned to show that such an important proposition as that of the existence of God can itself be proven by the method, and not merely by a posteriori means. He may also have wanted to insinuate that whatever doubts might be raised concerning his arguments for the existence of God in Meditations III, anyone who is willing to accept proofs in geometry ought by the same token to accept this proof, which is based the same kind of analysis of ideas.

c. The rehabilitation of the mathematical sciences. Indeed, Descartes took the proof of God’s existence to not only be as certain as any other proof in geometry or mathematics, but to be foundational for all of those proofs. We might think that, if we know that the ideas of extension and its modes are real and true, then, whatever we can clearly and distinctly perceive about those ideas, as codified in the mathematical sciences, would constitute an independent body of absolutely certain truths. But Descartes claimed that the proof of God’s existence underwrites our certainty of all other demonstrative proofs in the mathematical sciences, so that were this important point not established in advance our certainty would be limited and incomplete.

To justify this claim, Descartes reviewed what he had established over the course of Meditations III-IV. The certainty produced by clear and distinct perception is transitory. It exists only for as long as the understanding is actually engaged in contemplating the particular ideas involved in the judgment in question. Under those conditions the understanding determines the will and we must judge accordingly. But when the understanding turns to contemplate other things, the will is no longer determined. In the absence of a continued determination of the will, and in the absence of a proof of the existence of God, doubts can creep in. We can note that we have made mistakes in calculation in the past and worry that we might just have made another one. Or we can worry that an evil genius might be deceiving us. Admittedly, these worries can be removed by returning to clearly and distinctly perceive the relation between the ideas involved in the judgment, which will produce an irresistible conviction, given that the understanding determines the will. However, this puts us in a difficult situation. The only way to preserve certainty is to constantly return to old proofs and contemplate them again, and the instant we turn to something else, doubt returns. Consequently, we end up being able to be certain of only a very few things: as many as we can manage to clearly and distinctly perceive at once. Worse, anything that can only be known by means of a long proof, requiring many steps or an appeal back to results established earlier, ends up being indemonstrable. No complex proposition is provable.

Descartes maintained that the proof of the existence of God removes us from this predicament. Once we have clearly and distinctly perceived that God exists, and have understood how far error on our part is compatible with God’s nature, we appreciate that God would not permit us to be mistaken about what we clearly and distinctly perceive, and would not allow any other being to trick us into thinking that we clearly and distinctly perceive something when we do not in fact do so. God may allow other beings to tempt us into error, but never about things that are clearly and distinctly perceived. And we ourselves may occasionally make errors in calculation, but as long as we are careful to frequently check our proofs we can trust that we will uncover the mistake. According to Descartes, this removes our doubts and allows us to be certain of the conclusions of demonstrations, even when we are not currently engaged in clearly and distinctly perceiving them. All we need to do is remember that we (repeatedly) clearly and distinctly perceived these matters in the past.

We might wonder about the efficacy of this solution. My certainty about some truth that I do not now clearly and distinctly perceive, such as that 786 x 13 = 10,218, is only as good as my memory that I did previously clearly and distinctly perceive this conclusion. But remembering that one has clearly and distinctly perceived something is not the same thing as clearly and distinctly perceiving it. Such memories can be mistaken. Indeed, we might speculate that when we make mistakes in simple sums, such as supposing that 7+5=13, this is always because we misremember what we clearly and distinctly perceived to be the case at some time in the past. Were Descartes to take things so far as to say that the goodness of God would never allow my memory to mislead me about what I have clearly and distinctly perceived he would be making a claim that is hard to accept, because I now remember that my memory has deceived me about arithmetical sums. If I am wrong about that, then my memory is now deceiving me. If I am not wrong, then it has indeed deceived me in the past. Either way it seems that my memory is untrustworthy.

A possible answer to this objection (though not one that Descartes himself offered in Meditations V) would appeal to the fourth rule of the method of Discourse II. Recall that rule four stipulates that we must make frequent reviews of our work. Remembering having performed a proof is not enough. We need to go back and perform the proof repeatedly. This could conceivably involve writing parts of the proof down and then reviewing those notes, considering them as a list of what steps we performed in what order. If, after repeated runs through the proof, we remain unable to discover any error, then we can recall (or prove once again) that God would not allow us to be deceived about any matter without having given us some capacity to discover our error. But beyond reviewing a proof over and over again, and using notes and other aids to our memory, there is nothing more we can do to assure ourselves of the correctness of a proof. So were we to still be convinced after frequent reviews of the proof, we can be assured that we would have done all we could to uncover a mistake in calculation or an error in remembering earlier steps, and we could think that the goodness of God would guarantee that the proof must be correct. (For an attempt to defend Descartes along these lines see John Cottingham, Descartes [Oxford: Blackwell, 1986], 71-72.)

We might object that even if I make frequent reviews of my work, I still need to remember that I did so, and even if I take down notes, I need to remember that those notes are mine. I could merely dream that I performed the proof over and over again when in fact I never did any such thing, and if I am now dreaming when I look at my notes, those notes may not actually record a previous effort at doing the proof.

Descartes’s answer to this objection would probably be that, having satisfied myself that God exists and is no deceiver (and only because I have satisfied myself of this), I can lay these sorts of extravagant doubts to rest. God would simply not allow me to be deceived about matters in which there is no hope of uncovering my error.

We might rest uneasy with this, and worry that even if there is no deceiver and even if my memory is generally reliable about certain sorts of things, it is far from being beyond all possibility that I might be now asleep and dreaming, utterly convinced that I repeatedly intuited results I never actually considered. But Descartes would be complacent about this and advise us to rest assured that, God being no deceiver, we will sooner or later discover our error if in fact we are making one. We will wake up and realize we were just dreaming. It would do well, in this context, to look ahead to the last sentence of the Meditations. “But because the need to get things done does not always permit us the leisure for such a careful inquiry, we must confess that the life of man is apt to commit errors regarding particular things, and we must acknowledge the infirmity of our nature.”

A great deal of emphasis is often placed on the claim that Descartes was an arch-foundationalist, who sought to rest all knowledge on a basis of absolute certainty. As a matter of fact (and as will be seen in more detail when we turn to Cartesian science) this picture is seriously mistaken. Descartes’s Meditations were meditations on first philosophy. (“First philosophy” is another name for metaphysics or the science that precedes physics.) The quest for certainty was a quest that Descartes engaged in only for a limited time and for a limited reason. He wanted to be sure of the most general principles. But, having established general principles, he was content to be less than certain about specifics and particular things. Indeed, on certain matters he was convinced that certainty is impossible and that we will never be able to do more than make conjectures. On the reading I would favour, Descartes would not have been distressed by the possibility that we might not be certain of the result of any complex demonstration because it would involve a reliance on memory of what has been clearly and distinctly perceived in the past. His response to such a situation would have been to say that in such cases we simply do the best we can and hope we get it right. We do not need to be absolutely certain that we have not been deceived. The fallible certainty that comes from remembering having reviewed the proof a number of times over is good enough. It is sufficient that we be absolutely certain just of the most fundamental things — indeed, just that we be assured that we could not be systematically deceived or mistaken about even the simplest and most fundamental things, such as the existence of God and the reality of extension.

ESSAY QUESTIONS AND RESEARCH PROJECTS

1. Do a comparative study of the employment of the notions of clarity/obscurity and distinctness/confusion by philosophers of the 17th and 18th centuries (in addition to Descartes, important figures to consider include Hobbes, Locke, Spinoza, and Leibniz, as well as the authors of seventeenth century logic textbooks that discuss these notions). Attempt to identify any significant divergences in the way these notions are understood. Look also at accounts of immediate or intuitive knowledge as they appear in the works of these authors and attempt to ascertain any connection there might be between the notion of clear and distinct perception and the notion of intuitive knowledge. Is it the case, for example, that clear and distinct perception simply consists in seeing one idea analytically contained inside of another and that it is this direct perception of containment that constitutes intuitive knowledge?

2. Assess the adequacy of Descartes’s attempt to defend his ontological argument for the existence of God against the objections he himself raises to that argument. Consider whether there are any other, more serious objections he fails to consider and then consider whether he could also answer those objections.

3. Based on a survey of Descartes’s remarks in the Meditations, Replies to objections to the Meditations, Principles of philosophy Part I, and in his correspondence, try to determine exactly what his position was on why we need to be assured of the existence of God in order to know other things, and what those other things are. Do I need to be assured of the existence of God before I can know any of the things I clearly and distinctly perceive, including my own existence, or just some of these things? Or is it rather the case that I need to be assured of the existence of God before Ie can be assured of the conclusion of a demonstration, but not of the truth of those things that I clearly and distinctly perceive without the assistance of a demonstration? Or is it just the case that Ie only need to be assured of the existence of God before I can be assured of the conclusions of demonstrations I am not now contemplating, but only remember having performed and clearly and distinctly perceived?

4. How serious is the following objection: At the close of Meditations V, Descartes claimed that a proof of the existence of God puts us in a position to rely on the memory of having clearly and distinctly perceived or demonstrated a truth. But, unlike clear and distinct perception, which is an act of the understanding that can arguably be considered to be infallible, remembering is an act of memory, and we know from experience that our memories are unreliable and can often perceive us. Moreover, the argument of Meditations IV does nothing to establish the reliability of memory (it only establishes the reliability of clear and distinct perception). Since we have good reason to doubt the reliability of memory, we still cannot rely on the truth of demonstrations that we only remember having performed, Descartes’s proof of the existence of God notwithstanding. Could Descartes have replied to this objection? If so, how? If not, might he still have been able to go on to say everything he did in Meditations VI or would his other conclusions be put in jeopardy?

5. Does anything that Descartes had to say in Meditations V help to answer the objection that there is a circularity in his demonstration of the existence of God in Meditations III?

6. How does the Meditations V argument for the existence of God differ from the Meditations III argument? Why is the Meditations V argument necessary? Might it just as well have been given in Meditations III or is there something about the Meditations V argument that makes it dependent on the results of Meditations IV? Is the Meditations III argument any less dependent on the conclusions of Meditations IV than the Meditations V argument?