Study Guide

Week Four: Descartes' Foundationalism - Finding Some Foundations of Knowledge

1. Materials Assigned for the Week
2. The Central Point of This Week's Material
3. Other Concepts and Points you are Expected To Master This Week
4. Miscellaneous Comments and Clarifications
   1. Before anything else, Give Each of Descartes’ Meditations a More Revealing Title
   2. Descartes’ "Foundationalist" Project as a Whole
   3. The Meaning of the Phrase "Clear and Distinct Ideas"
   4. Descartes’ Argument for the Existence of God: Meditation Three

I. Materials Assigned for the Week

Reading:

Lecture 13: Descartes' Foundationalism (concentrate on pp. 161-169)
Readings: Descartes, Meditations on first philosophy, Meditations 1-3, pp. 211-232. (pace yourself)

Exercises:

Review Questions: pg. 174
Problems for Further Thought: pp. 174-175

II. The Central Point of this Week’s Material

Descartes claims that some statements satisfy the conditions of the "stronger" definition of knowledge of Week Three, Knowledge = true belief logically immune to error.
He also claims he has a method for coming up with them, three in particular: "I exist", "I am essentially a thinking thing; my body is not essential to my being who I am", "God exists and is not a deceiver". These he makes into "foundational" items of knowledge. Upon them he proposes to rebuild the edifice of our everyday claims to knowledge of the physical world ("I am typing on a keyboard"), in the teeth of the sceptic's objection that there can be no such knowledge (only the likes of "I am mentally aware of whitish patches and pressure points").

III. Other Concepts and Arguments You Are Expected to Master This Week

• How to spell "Descartes" - the "s" is part of his name, so spell the possessive "Descartes' so and so" with the apostrophe after the "s" and not between the "e" and "s"
• What foundationalism is, in epistemology and also in geometry
• What the Method of Doubt is and why Descartes believes that it delivers foundational truths
• What the "Evil Genius" Hypothesis is (pp. 216-218) - what work is this hypothesis supposed to do for Descartes?
• In Lecture 31 - not part of the course - Sober discusses a modern equivalent of Descartes' Evil Genius Hypothesis, the "Brains in a Vat" Hypothesis (pp. 446-447) - you might like to compare the work which this device is supposed to do with the work the Evil Genius is doing
• The equivalence, for Descartes and others, of "foundational" and "indubitable" - in essence this amounts to another key definition in Descartes' epistemological project:

  "X is foundational if and only if X remains as residue after every logically possible attempt to doubt it has failed"

• What the famous maxim "cogito ergo sum" means, and why it is so important in Descartes' scheme of things
• How to apply the Method of Doubt to determine whether the likes of
  • "I exist"
  • "I am thinking" (i.e. "I am conscious")
  • "I am a thing that thinks" (i.e. "I am essentially a non-bodily thing")
  • "I seem to see a off-whitish shape in my visual field right now"
  • "There is an off-white keyboard in front of me"
  • "God exists"
  • "God is not a deceiver"
  • "Subjectively clear and distinct ideas deliver truths about the world beyond the world of our private mental experiences"
  • "What is past cannot be undone"
  are really undoubtable or doubtable / foundational or non-foundational
• The difference between minds and bodies - Descartes sets out at least four fundamental differences (keep track of them as you read the Meditations, but do this lightly; we return to the issue with a vengeance in Week Seven)
• Why everything mental is incorrigible (not capable of being doubted by me or corrected by another) and everything physical is corrigible (capable of being doubted and corrected) - and of course what this means for Descartes' foundationalist project as well as for the very distinction between minds and bodies
• What clarity and distinctness is in ideas
• The difference between clarity and distinctness considered as a purely subjective characteristic which mental ideas possess of and in themselves, and clearness and distinctness considered as a guarantor of the real existence of whatever extra-mental thing some idea is the idea of
• What the "inner" / "outer" gap is which the sceptic exploits and which Descartes seeks to close - this is especially important, if you don't understand it, you won't be able to understand much else of what is going on here (for help see IV.B below)
• The difference between the objective reality of an idea in my mind (the amount of reality which the object that my idea is an idea of has) and the formal reality of an idea in my mind (the amount of reality which my idea has in its own right simply as existing in my mind) - Descartes uses a parallel distinction between the "objective perfection" and the "formal perfection" of my idea of God to prove that a real God exists

IV. Miscellaneous comments and clarifications

IV.A Before anything else, give each of Descartes' Meditations a more revealing title

The titles of the individual Meditations as they appear in the "Readings" part of Sober are Descartes' own. They do not always make it very plain what Descartes is actually up to however. I can see no reason for making their work as plain as possible, right in their very titles. I would suggest you scribble up your textbooks accordingly:

• Meditation One: Descartes' "Method of Doubt" - what it is meant to show and how it works
• Meditation Two: Descartes' proof that only knowledge of immediate subjective experience is foundational.
• Meditation Three: Descartes' proof that a perfect God exists and is not a deceiver.
• Meditation Four: The true source of human error.
• Meditation Five: Practice exercises using the notion of a "clear and distinct" idea.
• Meditation Six: Descartes' method for getting from knowledge of one's private subjective experience to knowledge of the public physical world.

IV.B Descartes' "Foundationialist" Project as a whole

As always with any philosophical argument or sequence of arguments, the very first question to ask is: "What is the problem?" The problem that Descartes' foundationalism tries to solve is that set by the sceptic. Well, what problem does the sceptic set? The sceptic says that there are some things we know and some things we don't; and that in order to come to know what we don't yet know we must justify it on the basis of what we do know. A "Foundationalist" approach to this question is to insist that there are some things we know in the strongest possible sense of "know": about them we have knowledge which it is logically impossible for us to be wrong about (see 3.IV.A). Such knowledge is "foundational". Everything else we claim to know must be built upon these bits of foundational knowledge. That is, whatever knowledge is not foundational must be derived by valid argument from knowledge which is. Descartes happily accepts this as his task. The rest of what he commits himself to doing - maybe not the details but at least the overall projects he thinks he is required to take on board - follow as night follows day.

• First, Descartes must find some foundations. And that means also inventing a method for finding them. This is the famous "Method of Doubt". He constructs a thought-experiment in which there is an Evil Genius intent to deceive him about every belief which it is logically possible for him to be deceived about. Why this peculiar thought-experiment? Because any belief which such a hypothetical Evil Genius can't deceive him about must be a belief which it is logically impossible to doubt or be wrong about. And those beliefs will be foundational in the strongest sense: logically immune to any possibility of error. When Descartes proceeds to apply this test, he finds that most of the beliefs he has ever held fail it. That doesn't mean they are false (of course). It only means they aren't foundational. The only beliefs that turn out to be foundational - i.e. pass the Evil Genius test - are "I think", "I exist", "I am a thinking thing not a physical thing", and every belief he has about his present conscious experiences. So he has his method for finding foundations, and a few examples of them. (Meditations 1 and 2)
• Second, he has to figure out some method to get from those bits of foundational knowledge to what he doesn't have such foundational knowledge of. Since the foundations are pretty well exclusively about his inner mind, basically the task is to find a method of getting from the "inner" to the "outer" - to statements which are not statements about his private conscious experiences but about the public physical world and other people. Descartes' unusual idea here is to base his method around the non-deceptiveness of God. (Most other anti-sceptical arguments don't employ God.) So his second job is to prove that a non-deceptive God exists. This is what he does in Meditation 3 and which we will be covering in Week Four. [Another proof appears in Meditation 5 but we shall skip it]. You do not need to agree that he has indeed pulled off proving the existence of God. Indeed, you don't need to know to the very last detail exactly how his proof works and what other assumptions it relies on. But you do need to understand at least the point of proving God's existence in Descartes' overall scheme of things. A non-deceptive God is required in order to provide the right bridging principle for getting between inner and outer.
• Third, Descartes needs to show, and you need to grasp, how a non-deceptive God actually helps Descartes pull it off. This is covered extensively in Week Five. The basic idea in advance is that the existence of an Evil Genius is logically incompatible with the existence of a perfect God. We have just proved that a perfect God exists. So we have also proved that the Evil Genius is a logical impossibility. However, if there is no Evil Genius, then we are obliged to find an entirely different source for our perceptual mistakes than some super-power ceaselessly tricking us in undetectable ways. Descartes lays the real source of human error squarely at our own doorsteps. Specifically at our free choice to push such God-given mental faculties as understanding and imagination and sensation beyond their natural limitations and hence beyond the purposes which God gave them to us for. For instance, when we freely rely on confused or obscure experience, or freely refuse to detect the detectable difference between imagination and sensation, or freely argue purely to pass the time, then of course we will make mistakes. Happily, if we can freely choose to push beyond the boundaries of our God-given faculties, we can just as freely choose not to push beyond them. When we choose that, mistakes are impossible. For instance, if we choose not to push understanding beyond its natural limitations and stick only to those ideas which the faculty of understanding has been given us to work on - namely ideas which are clear and distinct - then any claim about the physical world which results will be well-justified and count as knowledge. Why? Because if in those situations we were still getting it all wrong, we could rightly blame God for creating us with systematically weird faculties and for misdirecting us about their boundaries. That is, God would have had to be a deceiver again.
• Fourth, it is always easier if we can find a shortish form of words for the bridging principle which Descartes has been building up to, and likewise a shortish argument form employing that bridging principle. We need the principle and we need the argument structure in which that bridging principle actually does take us from knowledge of so and so inner conscious experiences to knowledge of such and such truths about the outer physical world. The bridging principle is usually called the "Clear and Distinct Ideas Principle" and is simple enough to state and memorise: "clear and distinct ideas are true". The argument form Descartes is now able to rely on is just as simple and memorisable:

  • Premise 1: I have a conscious idea X present in my mind.
  • Premise 2: Idea X is clear and distinct.
  • Premise 3: Clear and distinct ideas are true.

  therefore

  • Conclusion 4: X is true of the public world outside of my private mind.

  Of course both the bridging principle and Conclusion 4 will often need to be phrased more carefully to fit each case. (We want the argument to take us from "I have a conscious experience of a rectangular patch of off-white in my private visual field" to "There is an off-white keyboard on my desk"; but surely we don't want to go quite so blithely from "I feel sick" to "The world is sick"!) The winning point of Sober's approach to problems of knowledge and scepticism - and one of the reasons we chose this text over so many others - is that such a refutation of scepticism is at least clear. It is clear what Descartes wants to do and it is clear how he sets out to do what he wants to do. His project therefore makes a nice introductory practice tool. Most treatments of scepticism don't.

IV.C The meaning of the phrase "clear and distinct ideas"

The need for a proper definition of what "clear and distinct" means first arises in the beginning of Meditation 3 (Sober pp. 223-224) when Descartes reminds himself that in Meditation 1 many things which he seemed to perceive clearly and distinctly enough were nonetheless not certain after all. For instance, the earth and heavens might be figments, and even something as simple as 2 + 3 = 5 failed to be immune to our ever getting wrong. True enough, Descartes definitely did have those ideas in his mind. But each time he also had other ideas inter-mixed with them: that the earth is something which exists outside of himself, that there was another being besides himself, an evil God, who could cause Descartes to err about 2 + 3 = 5. So the ideas of "earth" and "2 + 3 = 5" in his mind were not clear and distinct after all.

Descartes defines what he means by "clear and distinct" ideas like this:

An idea is clear when I have all of that idea before my mind.

An idea is distinct when I have nothing else but that idea before my mind.

This definition is elaborated in the general textbook Descartes wrote right after the Meditations, named The Principles of Philosophy (1644):

"I call a perception 'clear' when it is present and accessible [in its entirety] to the attentive mind - just as we say that we see something clearly when it is present to the eye's gaze and stimulates it with a sufficient degree of strength and accessibility. I call a perception 'distinct' if, as well as being clear, it is so sharply separated from all other perceptions that it contains within itself only what is clear [i.e. nothing else but itself]." "For example, when someone feels an intense pain, the perception he has of it is indeed very clear, but it is not always distinct. For people commonly confuse this perception with an obscure judgement they make concerning the nature of something [else in addition to the pain] which they think exists in the painful spot and which they suppose to resemble the sensation of pain; but in fact it is sensation alone which they perceive clearly [i.e. have the whole of]. Hence a perception can be clear without being distinct, but not distinct without being clear." (Principles, part 1, numbers 45-46)

Clarity and distinctness is therefore not, quite, a matter of the subjective vividness versus the subjective fuzziness of some idea we have. It is more a matter of the "boundaries" of the idea, as it were.

1. The whole of the idea must be immediately present and accessible to your mind. You have all of it. No bits of the idea have been left out. That makes the idea "clear". This is what does happen when you feel an intense pain. You feel the whole of that pain - there are no parts of the idea of pain which are not yet present (it's not that the pain is also, say, warm or soft, but you do not feel that part, you feel all of the pain, the whole thing). That's why intense pain is a "clear" idea.
2. As well, the idea in your mind must be so sharply separated off of all other ideas that it contains none of those other ideas mixed up in it. You have no other ideas except that idea before you. That makes the idea "distinct". This is what does not happen even when you feel an intense pain. You feel the whole pain all right, but your mind has other ideas "stuck to it", as it were, so you don't have only the feeling of pain. For instance, you also have the idea that there exists something at the painful spot (a knife, a match, a fist); this is not itself the feeling of intense pain, but an extra judgement you make, about what's happening at your epidermis rather than what's happening purely inside your mind. It takes great training - not unlike that needed to be become a decent painter - before one is able to strip off these extra judgements and get down to the intense pain unmixed with anything else. So even an intense pain is not, usually, "distinct" enough to satisfy the "clear and distinct" rule.

In those cases where some idea does satisfy both of the conditions of clearness and distinctness, then we seem to be on to a very powerful principle indeed, one which can be turned directly against the sceptic. In fact, we are on to the very bridging principle from "inner" to "outer" which Descartes has been looking so hard for. Here is how he argues at the beginning of Meditation 3, when he recalls the cogito results of Meditation 2, results which do meet both conditions:

"I am certain that I am a thing that thinks. But do I not therefore also know what requirement must be met in order that I may be certain of something? Surely, in this first instance of knowing, there is nothing else than a certain clear and distinct perception of what I affirm [viz. that "I am a thing that thinks"]. Yet this clear and distinct perception would hardly be sufficient to render me certain of the truth of a thing, if it could ever happen that something that I perceive so clearly and distinctly were false. And thus I now seem to be able to posit as a general rule that what I very clearly and distinctly perceive is true." (pg. 223)

The reasoning here is quite straight-forward.

• Premise 1: I know X.
• Premise 2: In order to know X, I must also know what are the conditions for knowing in general (the conditions which X must have satisfied in order to be known).
• Premise 3: The only condition met by the case X is clearness and distinctness of the idea X (I had the whole of that idea and I had no other ideas mixed in with X).

therefore

• Conclusion 4:Clearness and distinctness are the conditions for knowledge.

This result might as well be called something Official.

Descartes' "Clear and Distinct Ideas Principle"

Whenever I make judgements about what is outside my mind on the basis of clear and distinct ideas inside my mind, those judgements are true.

If Descartes has all this on page 223, why isn't his Foundationalist Project over and done with right here, at the very beginning of Meditation 3? Why all the palaver about the existence of God in the rest of that Meditation? And why three more Meditations to follow that? (Another 29 pages!)

• First, even were the argument to Conclusion 4 impeccable, it might still be wrong. Certainly it is not automatically immune to the Evil Genius deceiving us about. The cogito ergo sum was indeed immune, for even if the Evil Genius did exist, it is still logically impossible for the Evil Genius to deceive me into thinking falsely that I was thinking (i.e. deceive me into thinking I was when I wasn't thinking), since of course thinking falsely is just more thinking. Not so with the clearness and distinctness business. It is perfectly possible for me to be deceived into thinking Conclusion 4 is true when in fact it is false. Indeed, that is precisely what the sceptic is challenging Descartes about. So long as there is any possibility that an Evil Genius roams the universe, the most that we can do is state the bridging principle which Descartes has been looking for. But we can't yet claim to know for sure that that principle is true.
• Second and more interesting, suppose that we did know such a bridging principle were true. That would still not be enough to get any results from it! We now have in hand the formula that will take us from inner to outer, we do not yet have a reliable technique for deciding whether we have arrived at one of those occasions where we can use it to do such work. Descartes' bridging principle has the general form "whenever X, then Y". It is an ordinary conditional: "if so and so, then such and such". But as with all conditionals, we can't know that the "then such and such" part has been justified unless we know that the "if so and so" part has been fulfilled. And that is exactly what we do not know … yet. After all, we are only at the beginning of Meditation 3. The beginning of Meditation 3 is far too early for us to claim we can decide reliably of some idea we have in our mind if it actually is clear and distinct or merely seems to be clear and distinct. That is, so long as the Evil Genius continues to be an ever-present possibility - albeit a "tenuous and metaphysical" possibility - it will not be possible for me to decide of one of my ideas whether I have the whole of it or whether I have just a bit of it. Nor - so long as the Evil Genius might still be at work - will it be possible for me to decide whether I have only that idea in my mind or whether I have it mixed together with other ideas as well. For all I know, as yet, such an Evil Genius might be concentrating all his trickery towards deceiving me about exactly that matter: into believing some idea in my mind is clear and distinct when really it isn't.

Example: "I have the idea of an earth and the heavens" (pg. 216). It is beyond all doubt that I do have such ideas in my mind. Their existence in my mind is not what is being called into question. However, while the Evil Genius lurks, it is not beyond all doubt whether I have other ideas intermixed with them, such as the idea that the earth is something which exists outside of myself. So it's not, yet, beyond all possibility of doubt that I do indeed have the whole of the idea of the earth and have nothing else but the idea of the earth present before me. To be confident that my idea of the earth is a clear and distinct idea, I need still to prove that a perfect non-deceiving God exists and hence that the Evil Genius does not exist.

Once the existence of God is proved, and thus the non-existence of an Evil Genius, then Descartes can rely on identifying which of his ideas are clear and distinct and which aren't. Directly he can do that, the "Clear and Distinct Ideas Principle" can be used to get from those ideas to knowledge of the physical world outside his mind. Until he can do that, however, the Clear and Distinct Ideas Principle will deliver no goods. The existence of God has to be proved next.

So that is exactly what Descartes does do next.

IV.D Descartes' argument for the existence of God: Meditation Three

The proof he offers has the logical form of an ordinary causal argument:

• Premise 1: X exists.
• Premise 2: only Y could have caused X.

therefore

• Conclusion 3: Y exists.

[There is a hidden premise in any such causal argument, namely that everything which exists must have been caused to do so - i.e. that the notions of existence and causation always go together. The Meditations never examine this assumption, so we shall flag it away too. Interestingly, however, it was the pivot-point of much debate in medieval proofs of the existence of God.]
Descartes' special take on the causal argument is that the item X which he chooses to concentrate on in Premise 1 is not a public physical thing but a private mental idea. He concentrates on this, of course, because he has just proved that it is only the existence of such ideas in his mind that he has foundational knowledge of. Here is his argument, still pretty simplified:

• Premise 1: I have in my mind the idea of a perfect God (a being who is all-powerful, all-good, all-knowing).
• Premise 2: Nothing less great than a perfect God could have caused that idea to be present in my mind - this is the causal part of the argument.

therefore

• Conclusion 3: There actually does exist a perfect God (outside my mind).

What typically causes problems for students in Week Four is not the basic structure of such a proof as this, but some of the concepts which Descartes brings in as he slowly refines Premise 2 so that it will convincingly deliver Conclusion 3. These are the sorts of concepts which Sober is dealing with on pp. 170-171 when he works on the concepts of the "objective perfection" of an idea of a thing and the "formal perfection" of the thing itself. Because there is often so much trouble here, let me work through some of these materials much more slowly.

If they've caused you no trouble skip this and rely on Sober alone.

Different things can have different kinds of reality

While all ideas exist as items in their own right, they also all represent other things than themselves. This provides Descartes with his first key notions: different "kinds" of reality. That reality can come in kinds will be news to most of you.
The two kinds of reality to be distinguished are:

• the objective reality which some thing possesses by virtue of its representing some other thing, and
• the formal reality which some thing possesses considered as a thing existing in its own right.

The notion of "kinds" of reality is best illustrated by an analogy. Take a painting of a dog. The formal reality which that painting possesses is the kind of reality it has considered just as an item made up of pigments and oil - as opposed to being a thing made up of, say, celluloid and silver or a thing made up of cells and bones. The objective reality which that painting possesses is the kind of reality it has considered as a representation or picture of a dog - as opposed to being considered as a picture of a stream or tree, say.

Different things can have different amounts of reality

Descartes' notion of "degrees" of reality is the notion that some things are more real than other things. This too will be unfamiliar to most of you, though not perhaps quite so hard to grasp. Think of yourself versus a mirror image of yourself - don't you have some temptation to think that the mirror image is somehow, in some way, less real than you are? Descartes bites the bullet. Some things indeed are less real than others. And this is not merely a figurative or diplomatic way of speaking: some things honestly have a smaller amount of reality than other things: my mirror image is less real than I am because it quite literally has a smaller chunk of reality than I do.

Some things have a greater amount of objective reality than other things. Some things have a greater amount of formal reality than other things.

The best explanation is to continue the analogy.

The first notion, that things can have different amounts of "objective reality" is familiar enough even now. A painting that represents a higher thing will have more "objective reality" than a painting that represents a lower thing. For instance, a painting of an angel has more "objective reality" than a painting of a rock, because a painting of an angel is a representation of a thing with more "formal reality" (namely a higher-ranking angel). The painting of a rock has less "objective reality" than a painting of an angel, because it is a representation of a thing with less "formal reality" (namely a lowish-ranking rock).

The other notion - that things can have different amounts of "formal reality" - while less familiar today, was well-worn in Descartes' time. Animate beings, for instance, are higher ranking in the scale of things than inanimate things - animate beings (dogs) possess a greater amount of "formal reality" than inanimate things (rocks), they are a higher "form" of thing. Likewise, dogs are a higher form of being than trees (both are animate, but dogs have the power of self-movement). Humans are a higher form of being than dogs (because they have rationality and not merely perception). Angels are a higher form of being than humans (because they have shed corporeality but kept their rationality). God is a higher form of being than angels (because angels are still limited in their power and knowledge and goodness).

Ideas in the mind can also have different kinds of reality and different amounts of reality

Descartes is not particularly interested in paintings, photographs, maps or other such familiar physical representations. He is interested in only one special kind of representation, that is, mental representations or ideas in the mind. But the two key notions carry over exactly to ideas. Ideas in the mind have both kinds of reality. They possess "objective reality" (insofar as they are representations of others things than themselves): an idea of a dog is a representation, a mental representation, of a dog. They also possess "formal reality" (considered as existents in their own right): they are, for instance, mental existents as opposed to physical existents, they have no power of self-movement through space, etc. Ideas in the mind have differing degrees of reality as well. My idea of a tree has less "objective reality" than my idea of a dog (because my idea of a tree is a representation of a thing, namely a tree, which has less "formal reality" than a dog has).

Descartes' crude causal principle

Using these distinctions, Descartes sets out to construct a causal principle which will eventually link private ideas to public things. He first lays out a more general causal principle which doesn't use these refinements. (Compare Sober, pg. 170.)

There must be at least as much reality in the cause of anything as there is reality in the effect.

After all, Descartes asks rhetorically (pg. 220), where can an effect get its reality from except from its cause, and how can the cause give reality to its effect unless it also has that reality (indeed, unless it has as least as much reality as it is giving)? This is an ancient principle, as Descartes notices: "You can't get something from nothing" (ex nihil nihilo fit); "What is more perfect can't come from what is less perfect"; "A pan of water can't be heated to a greater temperature than the fire that heats it"; "A stone cannot come into existence unless it is produced by something at least as real as a stone is"; "A hydrogen atom can't come into existence out of nothing at all in empty space (denied by Fred Hoyle's "Steady State" theory of the universe in modern astrophysics).

Such a causal principle begins to expand Premise 2 of the simplified proof:

• Premise 1: I have in my mind the idea of a perfect God (a being who is all-powerful, all-good, all-knowing)
• Premise 2: An effect can be brought about only by a cause which has at least as much reality as the thing it causes
• Premise 3: The idea of God in my mind is perfectly real
• Premise 4: Nothing less great than a perfect God could have caused that idea to be present in my mind

therefore

• Conclusion 5: A perfect God actually exists.

The problem with this crude causal principle, however, is that the main examples which Descartes uses to illustrate it with are patently not ideas in the mind as promised but ordinary physical objects: stones, stoves and pans of water, hydrogen atoms.

Descartes' refined causal principle

What Descartes needs is a version of such a causal principle designed specifically for the production of ideas in the mind. This is where the refinements in terminology earlier finally take their proper place:

There must be at least as much formal reality in the cause of an idea in the mind as that idea has objective reality.

(Compare Sober, pg. 171.) Such a causal principle can be illustrated by a chart of allowable causes of some idea in my mind:

Take any idea in the mental idea box. Circle it. Draw a line under that idea and continue the line under the thing at the same level in the thing box. The causal principle is that no thing below that line can be the cause of that idea. Simple. Now translate that into Descartes' technical terms. The line under the mental idea is a line under an item with so and so amount of "objective reality". The line under the thing at the corresponding level is a line under an item with the same amount of "formal reality". Hence the principle: no thing with a lower amount of "formal reality" can be the cause of a mental idea with a greater amount of "objective reality". Simple.

Example: Take a mental idea of a tree in the first box. Circle it. Draw a line underneath it and continue that line underneath the thing at the corresponding level in the second box.

The point of Descartes' causal principle is to insist that nothing lower down than a tree could possibly cause the idea of a tree in me, though a tree or anything higher than a tree could. No amount of looking at inert, inanimate, unchanging rocks, for instance, could ever cause me to have an idea of a tree - that is, an idea of an animate, self-replicating being, whose parts each perform a different job for the whole at different times - with roots and branches and seeds, dropping its foliage in the fall, adding one growth ring per year and so on. But I myself could cause that idea in me - since I am a being higher up the list than a tree: I could invent it for myself in a fantasy or science fiction story. Likewise, angels could implant such an idea in a mind for the first time too, in the dream of someone who had never been out of the desert, say. But definitely nothing below the line of trees.

Descartes' survey of ideas in his mind

Immediately after giving his new causal principle, Descartes surveys a range of ideas that exist in his mind (pp. 227-228). The survey nicely illustrates the causal principle just used.

• Some ideas I have represent corporeal animate beings (e.g. my idea of myself) - such ideas could be caused in me by corporeal animate objects, or by angels, or by God.
• Some ideas I have represent corporeal inanimate objects (e.g. my idea of a block of wax) - such ideas could be caused in me by corporeal inanimate objects (wax), or by corporeal animate objects (people), or by incorporeal animate objects (angels), or by God.
• Some ideas I have are so vague (e.g. my idea of heat and cold), that it is hard to say what they are representations of, if anything (whether heat is a privation of cold, or cold is a privation of heat, or whether both are properties of things or neither is, or whether both are actual things or neither is) - for such ideas it is not necessary to assign any cause other than my own mind.
• Some ideas are the clear and distinct elements of ideas I have of corporeal things (e.g. my idea of spatial extension) - their cause too must be something with at least as much "formal reality" as those ideas have "objective reality", any corporeal thing could be their cause, so could anything higher in the list, but probably I am that cause.
• This leaves the most important of the ideas I have in my mind: the idea of a perfect God (pp. 228-229). This is the idea of "an infinite and independent substance, intelligent and powerful in the highest degree, who created me along with everything else". [Descartes spells out "perfect God" in the traditional way: a being who is all-powerful (omnipotent), all-knowing (omniscient) and all-good (omnibenevolent). Spelled out this way, "perfect being", "infinite being", "infinite substance" are pretty much interchangeable.]

The cause of my idea of a perfect God

What could be the cause of that idea in me? The earlier boxed principle applies here too.

Because my idea of God possesses the highest possible amount of objective reality, it must have been produced in me by a being with the highest possible amount of formal reality, namely God.

Descartes doesn't actually repeat this formula in so many words, but what he does say is close enough:

"The idea of substance in me ... would not for that reason be the idea of an infinite substance, unless it proceeded from some substance which is in fact infinite." (pg. 229)

"I understand by the word 'God' an infinite and independent substance, intelligent and powerful in the highest degree, who created me along with everything else ... all these qualities are such that the more diligently I attend to them, the less they seem capable of having arisen from myself alone. Thus, from what has been said above, we must conclude that God necessarily exists." (pp. 228-229)

As before - as always - the point of the refined causal principle is to insist that nothing lower down on the things side can be the cause of an idea on or above the line on the ideas side. So nothing lower down than God can be the cause of my idea of God. Only an actually existent perfect God has enough "formal reality" to cause me to have an idea in my mind with as much "objective reality" as the idea of a perfect God.

This completes the official proof of God's existence in Meditation Three:

• Premise 1: I have in my mind the idea of a perfect God
• Premise 2: An idea can be put into my mind only by a cause which has at least as much formal reality as that idea has objective reality
• Premise 3: The idea of a perfect God has an infinite amount of objective reality
• Premise 4: No entity which possessed less than an infinite amount of formal reality could have caused that idea
• Premise 5: The only entity which has an infinite amount of formal reality is a perfect God

therefore

• Conclusion 6: A perfect God actually exists.

Why I myself can't be the author of my idea of God

Descartes doesn't dwell on this simple argument structure for very long, however. Instead, he immediately moves to examine several reasons why that idea couldn't have been made present in my mind from anything less than a perfect God - in particular, why I myself, a finite substance, couldn't possibly be the author of the idea I have in my mind of an infinite substance (pp. 229-230).

Add to your toolkit!

This is good philosophical procedure. No matter how impeccably some general principle may have been arrived at, it should always be tested against the rough and tumble of examples and counter-examples.

1. For a start, Descartes insists that I mustn't think that I could have produced the idea of a perfect God by performing sort of process of "negating the finite". This is a confusing turn of phrase, but the idea is simple enough. I can produce the idea of rest and dimness by negating the ideas in me of motion and brightness caused by moving bright objects. But I could never produce the idea of an infinite being by negating the ideas in me of finite beings. Indeed, there is no way I can construct the idea of any infinite and perfect X by any examination of my ideas of finite and imperfect Xs. For how can I know that some idea was of a not so perfect such and such if there were not already present in my mind an idea of a more perfect such and such - "by comparison with which I might acknowledge such defects"? I get the idea of a perfect X first. I get the idea of an imperfect X only second. Once I have the idea of a perfect X, then I can reason that some other idea falls short of that perfect X in some respect. This is the only way I can ever construct the idea of an imperfect X - by comparing it to a perfect X. This means I can never get the idea of a perfect X from any ideas I have of imperfect Xs; the procedure always works the other way around: "The perception of the infinite somehow exists in me prior to the perception of the finite". (This sequence - imperfect constructed from perfect, not perfect constructed from imperfect - goes back to Plato; Descartes takes it for granted; the later so-called "British Empiricists" strongly criticised it.)
2. Nor should I think I could have produced the idea of a perfect God because that idea does not after all possess anywhere nearly as much "objective reality" as the grand words "perfect God" might suggest. This sometimes happens, that my ideas have less objective reality than I initially suppose they have. Descartes says this is the case with such ideas as hot and cold. If my idea of a perfect God were like my idea of hot or cold, then it would be a representation of something whose "formal reality" is so indeterminate that practically anything could be the cause of it, especially a being with as much "formal reality" as I myself possess. However, the idea I have in my mind of a perfect God is not at all like the idea I have in my mind of hot and cold. The idea of a perfect God "is the most clear and distinct of all ideas and contains more objective reality than any other idea".
3. Finally, I shouldn't think that I could have produced the idea of a perfect God because I myself am actually a greater being than I commonly suppose I am (and therefore possess more formal reality than I commonly allow myself, indeed quite enough to match even the objective reality of such an idea as a perfect God). True enough, Descartes grants, my knowledge does gradually increase and has the potential to be even greater than it is now, so maybe it's true each of us does tend to underestimate ourselves. But that's exactly what rules me out as the cause. The idea in my mind of a perfect God contains no element of increase or potential; that is, it is not a mental representation of something which could increase or become greater; indeed, those are imperfections. So the cause of my idea must be something greater than anything which possesses scope for increase or improvement or betterment. And that means something greater than myself for sure. The cause must be something which is not merely potentially perfect. It must be something which is actually perfect. And that something is God.

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