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René Descartes: Search for Certainty

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Marc Bobro

on 15 September 2014

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Transcript of René Descartes: Search for Certainty

What was Descartes' solution?
look at the
second
sentence of the first meditation...
Check out the first sentence of the first Meditation:

 Several years have now passed since I first realized how numerous were the false opinions that in my youth I had taken to be true, and thus how doubtful were all those that I had subsequently built upon them. (AW 40)
Descartes' approach here was not altogether unique. The atmosphere in his time—the 17th century—marked the beginning of a new age. Mind-boggling imagination, discovery, theory in all intellectual areas, especially in philosophy and science. The microscope was invented and used; the telescope became popular.
Descartes' biography...
I had an epiphany. When I (Descartes) was younger I believed so many things that now seem to me to be clearly false.
 
As a consequence, I was forced to place great doubt upon any belief based on these false beliefs.
 
What could I do but to start anew and build from the ground up, so to speak?

And thus I realized that once in my life I had to raze everything to the ground and begin again from the original foundations, if I wanted to establish anything firm and lasting in the sciences. (AW 40)

Note the term 'sciences' here. Like Bacon, one of Descartes' chief goals in the Meditations is to provide warrant for science, whether it's physics, astronomy, biology, etc. His search for certainty is not merely a philosophical problem; it has an important practical aspect.

This is an enormous task, so I had to wait till I was truly ready. Now I am.

There is a wee problem, however—I have so many beliefs, I couldn't even hope to go through every single belief and demonstrate that each and every single one is false.

Descartes believes that he has found such warrant. In the
Meditations
, he reports this good news as a kind of autobiographical path to such discovery. (As opposed to a logical path.) We are asked by Descartes to meditate along with him.

René Descartes: Search for Certainty
Now, 250 years or so before the 17th century, the Middle Ages came to an end. In Europe at least, the Middle Ages were
theocentric
. Common faith, religious practice, and the Church, guided and shaped society. There also was a unity between theology and philosophy. But this relationship was beginning to dissolve, just as the relationship between Church and state was dissolving...

Theology as "queen of the sciences" slowly eroded, accompanied by a separation of philosophy from theology. This allowed greater effort to explain things rationally without first invoking divine causality for the successful workings of nature. Philosophers sought (and Descartes was no exception) new grounds for certainty and knowledge. For this reason, the modern era is thought of as thoroughly
epistemological
in spirit.

Church & State: Nicolo Machiavelli (1469-1527)
Church & Institutional Authority: Martin Luther (1483-1546)
Church & Faith: Ockham
Church & Science: Galileo
So the problem is this: philosophers sought certainty, but where was certainty going to come from?
It seems reasonable to simply reject any belief of mine, or not believe in anything, if it is not completely certain. In other words, if an opinion can legitimately be doubted, I'm going to reject it.

Still, there are so many of them, I can't run through them one by one....

So looking only at beliefs based on sense-experience, I remember that occasionally I have been deceived by my senses.
 
But is it really reasonable to trust completely anyone who has deceived us before?
 
Just as we throw out the entire testimony of a perjurer, so should we reject all beliefs of a particular kind if a portion of those beliefs has been determined to be false.

You reply: this is too fast, my dear Descartes—sure, some of our beliefs based on sense-experience have turned out to be false, but this can easily be understood in terms of our own physical limitations.

You continue: there are many sense-beliefs, however, that are not deceptive, and where doubt of their truth seems absurd (e.g., those close-up, intimate sense-beliefs). The only people who do have false beliefs about such intimate details are the insane, drunk, or drugged. Are you, Descartes, saying that we're all mad, or drunk, or drugged?

No, I'm not (Descartes answers): for I can think of at least one kind of situation where a perfectly rational person can decide to hold close-up, intimate sense-beliefs in a seemingly perfectly normal and rational manner yet it turns out they are entirely false. I am thinking of course of the phenomenon of DREAMING.

"I see so plainly that there are no definitive signs by which to distinguish being awake from being asleep" (AW 41). But what
exactly
does Descartes mean by this?

(a) that we cannot tell that we are dreaming when we are in a dream-state? and/or


(b) that we cannot tell that we are not dreaming when awake?

Just (a), as I (Descartes) will talk about in my final Meditation. Think about it, (a) is all I need to make my point! The question is whether rational people can come to hold "intimate" sense-beliefs that turn out to be false, so all I need to show is that in dream-states this very thing happens. Whether or not we realize the belief is false upon waking is irrelevant.

You might reply: but, Descartes, it seems that I don't really have proper beliefs during my dream-states. Yes, I have sense "impressions" or "observations," for example, of a river and my hand cupping its running water, but these are not
bona fide
beliefs.

Descartes continues:
 
You find my claim that there are no "sure signs" to tell that we are dreaming when we are in a dream-state far-fetched? Well, consider dream-states—even the most wildly fictitious dream, like the strangest painting you've ever seen, is still composed of real elements (or at least elements found in our awake-experience).
 
So, the fact that we dream casts doubt on a
large number of beliefs, all those sense-beliefs
that posit the existence of specific kinds of
composite objects.

What beliefs remain untouched?


Well, belief in the basic extended nature of things, that there is shape in the world, that there is quantity, that there is size, that there are numbers of things, and the space and time in which things exist and endure. (In other words, the fact that we dream places no doubt on the belief that there is a world external to us, though it casts doubt on our particular beliefs about the particular way the world is
constructed
.)

This means, of course, that physics, astronomy, medicine, biology (and
any
discipline which depends on the study of composite things) are doubtful and sense-beliefs in those fields rejected.

Bummer, because look again at the second sentence of Meditation One...

Truman Show, The Matrix, Lem's Brain in a Vat story, etc.
At least there is something that is
not
placed in doubt. Besides the mere fact that there is a world, we can still trust in arithmetic, geometry, and other subjects of this kind "which deal only with the simplest and most general things, regardless of whether they really exist in nature or not …. For whether I am awake or asleep, two and three added together are five, and a square has no more than four sides" (AW 42).

These are "transparent truths." Wait ...
are
they?

For now we get to Descartes' DECEIVING GOD hypothesis:

I (Descartes) have believed, for a very long time, that God exists—a God that created me and is all-powerful. But how do I know that he is not deceiving me even with regard to things wholly untouched by the doubt cast by the dreaming argument?

Before we begin, let’s talk about doing history of philosophy. We would do well to heed Descartes’ own words:

"I should like to beg future generations never to believe that I am the source of an opinion they hear unless I have published it myself. I do not wonder at the absurdities attributed to all the ancient philosophers whose writings we do not possess; nor do I conclude from these attributions that their thoughts were highly unreasonable." (CSM I, 146f)

Let's also talk about the difference between doing
historical
history of philosophy and
philosophical
history of philosophy.
What are some things that you used to believe with great confidence but now do not?
Perhaps there is no world at all! No earth, no sky, nothing even that's extended! So no shape, no size, no location. Yet all this time God might be allowing (or better, causing) me to believe that such things do in fact exist.

What about mathematics and geometry, whose propositions are rooted in pure reason? Well, why couldn't God have caused to me to go wrong even here?

You object
: but God is all-good as well, so he would not have allowed you to be deceived in this way....
Descartes' reply:

Don't we believe that his goodness is not compromised by the fact that he allows us to be deceived sometimes? If so, why should his goodness be compromised if he allows us to be deceived all the time? If constant deception is incompatible with perfect goodness, then shouldn't also intermittent deception be incompatible? Descartes continues:

Let's then suppose that God doesn't exist. But think about it, would it not be even more probable that I am being deceived on such a supposition? For my original cause—"the author of my origin" (AW 42)—would be less powerful and thus less able to keep me from being deceived.

It seems that I am in a terrible epistemological funk. "I cannot possibly go too far in my distrustful attitude."

So, to continue with the "general demolition of my opinions" (AW 42f) I'm going to suppose that there is some EVIL GENIUS (malicious demon) using all of his many powers to deceive me. Sky, air, earth, colors, shapes, sounds and all external things are mere delusions. I don't even know that I have hands, eyes, flesh, blood, or senses at all.

Interestingly, there is no mention of mathematical judgments here. Why not?
THE END OF MEDITATION ONE
Descartes ends:
"I am not unlike a prisoner who enjoyed an imaginary freedom during his sleep, but, when he later begins to suspect that he is dreaming, fears being awakened and nonchalantly conspires with these pleasant illusions" (AT 43).

Descartes is tempted to rid himself of the desire to acquire knowledge altogether.
MEDITATION TWO

Descartes still holds out some hope for great things if he can manage to find just one thing. It doesn't matter what it is or however inconsequential. What matters is that it is certain and indubitable (i.e., cannot be doubted).

Read the so-called
Cogito—
"I have convinced myself that ..." (¶ 3)

Actually the famous
cogito ergo sum
(I am thinking therefore I exist) doesn't appear in the
Meditations
. You will have to look to Descartes'
Discourse on Method
and
The Principles of Philosophy
(I, 7).

Compare with Montaigne's
dubito ergo sum
(I am doubting therefore I exist) and St. Augustine's
fallor ergo sum
(I am being deceived, so I exist).

What exactly is the Cogito?
Is it a SYLLOGISM?

1. Everything that thinks exists. (implicit premise)
2. I am thinking.
Therefore
3. I exist.

Problem one—how can we possibly know that premise one is true given the state of knowledge we're in at the end of Meditation One? And of course Descartes doesn't give premise one. Problem two—in the second set of Replies, Descartes insists that the meditator need not construct a valid syllogism with an implicit major premise. In fact, "it is in the nature of our mind to construct general propositions on the basis of our knowledge of particular ones" (CSM II, 100).
An IMMEDIATE INFERENCE?


I am thinking; therefore, I exist.

The idea is this: Descartes simply recognizes or reasons in his own particular case that it is impossible that he should think without existing. That is, a valid inference with only one premise.

A problem with this interpretation and the previous is that both assume a certain view of logic, but wasn't even this put under doubt by the deceiving God hypothesis? There's another interpretation possible, however.
A PERFORMANCE?

I am thinking, I exist.

Here, what's really important in uncovering the certainty of his existence is not an abstract piece of reasoning, but rather an individual act of thinking.

PROBLEMS!
1. Given that the most powerful God ever conceived by a philosopher might be deceiving me, can I even assume that thoughts need a thinker? Perhaps there can be "floating" thoughts (as David Hume seems to have believed)!

2. Also, does the Cogito escape the net of doubt cast in Meditation One? Descartes says that judgments about his own thoughts are entirely unproblematic (indubitable). Mental states are epistemologically transparent. (See ¶ 8).

3. Even granted the transparency of mental states, there is a problem of identity over time. Descartes says: "Am I not the same who now doubts nearly everything, who still understands something; who affirms that this one thing is true?" But how do I know that there is a single entity that is the subject of all my thoughts? Perhaps, a host of subjects, or a chain of subjects taking over the thinking from one moment to another!

Descartes makes five main claims in Meditation Two:

1) I think
2) I am a thinking thing
3) Thought is a property essential to me
4) Thought is the only property essential to me (besides unity and duration)
5) I am essentially a thinking thing, and not essentially material

It
sounds
as if Descartes is right then I have a very good understanding of what I am, something that indeed is not material at all. But can this be right? I cannot help but think that I know bodies much better than this "puzzling 'I' " which cannot be pictured in the imagination.

In fact, if Descartes is right, then not only do I know the nature of the mind better than that of the body ...

Thus, Descartes has two aims in Meditation Two:

(a) that we can know with certainty that we ourselves exist even without knowing that bodies exist or the truth of particular mathematical propositions, and,
(b) that we have an understanding of the nature of body which is far superior to what we take to be knowledge gained by direct sense-experience.

(This is precisely the main point of his famous wax example (AW 45f).)

MEDITATION THREE
Descartes pauses for reflection at the beginning of Med. 3 (AW 47):

What do I know?

Whether or not he has access to things outside of himself, Descartes is confident that he has the POWER to SENSE such things and the POWER to IMAGINE (have images of such things).

But Descartes wonders what is required for him to be certain of anything? Well, let's see … in the case of the Cogito, Descartes says: "I saw very clearly [and distinctly] that to think one must exist" (AW 47). Descartes proceeds in the following way:

What is required for knowledge is my simply having a CLEAR AND DISTINCT PERCEPTION of what I am asserting.

Provisionally therefore, Descartes lays down the following as a general rule: "everything I very clearly and distinctly perceive is true" (AW 47). Or in other words, whatever the natural light shows me is true (AW 49).

Not so fast! ... Descartes himself recognizes that he must address a serious problem:

But there is one last hurdle to assure myself that this rule may stand—that it is reliable
across-the-board
—I must be sure that God, supposing he exists, is not a deceiver.

So, Descartes needs to show that God exists and that he is not a deceiver.
This is how Descartes argues:
To show that God exists, let's make some distinctions. I have IDEAS (which themselves cannot either be true or false). Only judgments can be true or false; ideas don't assert anything, they're just there. There are three kinds of ideas: INNATE (that I’ve always had), ADVENTITIOUS (that come to me “unexpectedly,” and those INVENTED by me.

I, Descartes, am concerned here only with the ideas which I take to be derived from things existing outside of me. How do I know that my ideas resemble thing existing outside of me?

Now, I have this idea of God (eternal, infinite, immutable, omniscient, omnipotent, creator of all things).
Do you?

You might object: is our idea of God really like an image? Descartes would reply: we shouldn't think of images as exact copies (i.e., our idea of God is not an
imago tabularum
. At any rate, Descartes continues his line of thought:

Isn't the idea of God objectively more real than any other idea I could possibly have? Even more than the idea of myself! (AW 49) It represents the greatest amount of perfection.

Objective = representative.
Formal = actual.

But is it not "
evident by the light of nature
that there must be as much [reality] in the efficient and total cause as there is in the effect of that same cause"? (AW 49). In other words, there must be at least as much formal/actual reality in the cause as there is objective/representative reality in the idea. (Let’s call this the Causal Perfection Principle.)

Now, take my idea of God. It has more objective reality than the idea of myself. So my idea of God must have come from something besides myself. In fact, it could only have come from something which have as much formal/intrinsic/actual reality as the idea of God has objective/perfective reality.

So what does all this really mean?
According to Descartes, each thing is "assigned" a degree of reality (which corresponds to its perfection, that is, its capacity to exist independently). God, of course, is at the "top" since he is the most perfect, most independent being possible and so has the greatest degree of reality.

Descartes spends much time arguing that the
idea of God could not have come from himself
or any other being besides God.

Finally, near the end of Meditation Three, Descartes writes:

The whole force of the argument rests on the fact that I recognize that it would be impossible for me to exist, being of such a nature as I am (namely, having in me the idea of God), unless God did in fact exist. God, I say, that same being the idea of whom is in me: a being having all those perfections that I cannot comprehend, but can somehow touch with my thought, and a being subject to no defects whatever. From these considerations it is quite obvious that he cannot be a deceiver, for it is manifest by the light of nature that all fraud and deception depend on some defect. (AW 54)

Descartes not only thinks that he has shown that the "idea [of God] is innate in me, just as the idea of myself is innate in me" (AW 53), but also that God is not a deceiver! Most of Meditation Three is spent on God's existence, and then Descartes makes an extremely quick statement (argument?) that God couldn't be a deceiver.

Big issue.

We can now see very clearly the so-called CARTESIAN CIRCLE: Descartes wants to remove the possibility that there can be a Deceiving God. To do this, he first argues that God exists and second claims that God couldn't be a deceiver. Now to show that God exists he says that he clearly and distinctly perceives a causal principle. And to show that God is not a deceiver he says that he clearly and distinctly perceives that deception is incompatible with perfection. But remember WHY Descartes is trying to prove that God couldn't be a deceiver—in order to validate his provisional general rule that he can trust clear and distinct perception!! See the circle?
Cartesian "circle"
Let's leave Meditation Three on two questions:
Question 1: Can Descartes answer the problem of the Circle, given what else he says in the
Meditations
?

Question 2: Is it possible for Descartes to really proceed philosophically while making no assumptions at all? Is the following recommendation at all possible to follow? "Beliefs are barriers to real change. Start with no belief, no metaphysics, no dogma. Start absolutely naked and nude, with no theology, no ideology. Start empty! That is the only way to come to the truth" (Osho,
Buddha, His Life and Teachings
).

MEDITATION FOUR
Meditation Three attempted to establish the trustworthiness of clear and distinct perception by showing that God exists and is not a deceiver.

Question
: What is the central problem that Descartes attempts to solve in Meditation Four? Very basically, what's his solution?



"I experience that there is in me a certain faculty [power] of judgment, which, like everything else that is in me, I undoubtedly received from God. And since he does not wish to deceive me, he assuredly has not given me the sort of faculty with which I could ever make a mistake, when I use it properly" (AW 54).

But of course Descartes
does
make mistakes—and must admit this. (
Note
: Descartes says that his errors, namely, making false judgments, are the
only
evidence of imperfection in himself. Convincing?)

The problem is to explain the possibility of error without supposing intrinsic defects in his faculty of judging (assenting to propositions). How does Descartes
solve
this problem?

Well, what does
judging
involve for Descartes?

Judging involves perception of the understanding plus a voluntary act of affirmation or denial towards what is perceived. In other words, it involves both the INTELLECT (the power to know) and the WILL (the power to choose).

Now it is only by the "concurrence" (combination) of these two causes that error can arise.
Not
by the understanding alone: "For by the understanding alone I perceive only the ideas of which I can make a judgment, and no error strictly speaking appears in it …."

So the INTELLECT is not itself directly the source or subject of error (AW 55). Nevertheless, it is limited/finite (that is, it lacks clear and distinct perceptions of a great many things).

(
Note
: Descartes tells us not to blame God for our finiteness: there is no reason why God should "place in a single one of his creatures all the perfections which he can place in others"—spread out the perfections, so to speak!)

However, the WILL is not limited, particularly not limited by the intellect (AW 56).

In fact, according to Descartes, the will (or free will) is the most perfect of our faculties or powers (AW 55f).

Important
: the more clearly the understanding perceives something, the more the will is impelled to affirm it, but this impulsion or compulsion is not external and in no way undercuts our freedom of choice. Indeed, as Descartes says, "the more spontaneously and freely did I choose it"! (AW 43) (This is reminiscent of St. Augustine.)

Now, when no reason "forces me in one direction rather than another" I experience INDIFFERENCE (the lowest grade of liberty) ERROR may arise. Read ¶9 (AW 56).

In such cases, the will is used incorrectly...

Discuss
—If there is supposed to be a gap between clearly and distinctly perceiving p and assenting to or accepting p, then what about those cases where we are extremely compelled to believe certain things? How can I not believe that 2 + 2 =4, for example?

Q: What do you think of Descartes' account of willing? It seems that on the one hand Descartes accepts DOXASTIC VOLUNTARISM (that beliefs are, for the most part, free, voluntary, or controllable actions) and on the other hand that the will can be compelled to believe.
MEDITATION FIVE

Descartes continues the treatment of the mind/body problem begun in Meditation Two.

However, Descartes remains content to set aside the question of whether bodies exist. He considers only which ideas he has of things existing outside of himself are distinct, and which are confused. This procedure is sufficient to determine "the essence of material things."

What does Descartes distinctly "imagine" in bodies? (Note the word 'imagine'; it's clear that he's dealing with ideas of external things, and imagination itself as we shall see requires an image on the brain.)

Extension
... The idea of extension also includes that of divisibility, has parts, size, figure, location, motion, and to these motions various durations.

And Descartes imagines (as he thinks you do as well) countless instances of these properties in bodies

This is nothing new, Descartes insists.
But there is a moral here:

I have countless ideas of things (that may or may not exist outside my own mind); however, in one sense at least "they are not my invention but have their own true and immutable natures" (AW 58).

For example, I imagine a triangle (which may or may not actually exist) but does not the triangle of my "mind's eye" have an essence, that is, a true and immutable nature? Importantly, it is not invented by me or dependent on my mind. Every triangle I imagine will share certain properties, and necessarily so.

This is true not just of triangles, but any other shape, for example, a chiliagon. Chances are that I have never encountered a chiliagon through my senses. But I can demonstrate certain properties of a rhombus...

Descartes continues:

These properties are not invented by me.
Why? These natures have implications that I did not foresee. Once I start imagining and thinking about these properties, I am not really in control of what further properties I might apprehend.

Now, Descartes can bring God to the table again, so to speak:

This rule applies not only to shapes and numbers and other things related to pure and abstract mathematics and geometry. It can also apply to anything. For example, why not to God? As long as I clearly and distinctly perceive a property in or of God, I must assent to the proposition that that property actually belongs to God. If so, then we have another proof for God's existence!



So Descartes comes up with another argument for God's existence. He insists that he has a clear and distinct perception that existence is part of God's true and immutable nature. Spelled out, his argument can be formalized like this:

1. God is (by definition) the supremely perfect being.
2. (I clearly and distinctly perceive that) if something lacks existence, it lacks a perfection.
Therefore
3. God doesn't lack existence.

On the basis of this argument (based on clear and distinct perception), Descartes says he is just as certain of God's existence as he is that the sum of the interior angles of a triangle is 180 degrees or that a mountain must have a valley.

A COUPLE OF FINAL ITEMS related to Meditation Five
Kant's criticism: Is existence really a property? (Consider the farmer and the "perfect" pig example.) Kant thinks no. Reply to Kant: So what if it didn't? Descartes would presumably respond that God is the exception to this rule.

Then Descartes talks about the problem of
memory
. How even though when we clearly and distinctly perceive something to be true, we can't help but believe it to be true. However, when remembering judgments we previously made, we can be mistaken even about things we think we clearly and distinctly perceive .

But, Descartes argues, this is not an objection to the view that while clearly and distinctly perceiving something to be true, we must assent to its truth, and will not go wrong in our judgments. Why?*



*The simple answer is that memory is not involved in such cases.)

CONCLUSION to MEDITATION FIVE

This theory of true and immutable natures is intended to provide a foundation for an
apriori
mathematical science as well as a sort of foundation for Descartes' version of Anselm's ontological argument.

Let's read the last paragraph of Meditation Five. To me, this demonstrates well that those commentators who suspect Descartes was a closet atheist are wholly mistaken. It doesn't seem just "tacked on."

MEDITATION SIX

According to Descartes, all that remains is (1) to examine whether the external world consisting of material things exists and (2) to demonstrate the real distinction between mind and body (i.e., that mind and body are independent substances, each of which can exist without the other)

Existence of Bodies
Descartes thinks he knows that it is possible that material things exist.

Q: How does he know this? Well, remember in Meditation Five Descartes arguing that he clearly and distinctly perceives the true and immutable natures of material things (extension, size, shape, divisibility, etc.)? He concludes from this fact that there is some reason to believe that there are things which instantiate or manifest these true and immutable natures (externally existing things that are extended, have size, shape, parts, etc.)

Bobro
Descartes was born in 1596 in La Haye (now called Descartes), France, and studied at a Jesuit college. Instead of becoming the lawyer he was trained to be, he enlisted in the military. While he was in the military, Descartes devised his intellectual dream and that was to rebuild philosophy from its very foundational principles in order to ground the sciences. Fearing persecution by Catholic authorities in France, Descartes spent most of his life in the Netherlands and in fact wrote most of his famous works there. Descartes contributed greatly not only to the discipline of philosophy, but also to mathematics and science. He died in Sweden at the age of 53, apparently because the cold climate combined with early morning conversations with Queen Christina of Sweden. […]
These are just some of the big names: Galileo, Bacon, Descartes, Pascal, Spinoza, Leibniz, Locke, Huyghens, Kepler, and Newton.
The existence of material things is also suggested by the power of imagination.

Q: What does Descartes mean by imagination? He says that it is "nothing else but an application of the power of thought to a body which is intimately present to it." But what does this really mean? Consider an example:

Take two things: a pentagon and a chiliagon. I can understand both (five-sided figured, thousand-sided figure). But can I imagine both? No, strictly speaking, only the pentagon. For imagining something requires that I "see it as if it were present before me." I can't do that with the chiliagon, try as I might: "imagination requires a peculiar effort of mind which is not required for understanding" (AW 48).

Not only that but imagination is not a necessary constituent of me (even if I had no power of imagination, I would remain the same individual, other things being equal).

All of this tells me (Descartes) that imagination and the content of the imagination depends on something distinct from myself, most likely material things. In other words, the best explanation of how imagination is possible includes the existence of material things.

But none of this is really to prove with certainty the existence of material things. Q: What is Descartes' proof? Well, he speaks of the kinds of things he imagines:

... I perceive by my senses that I have a head, hand, etc., making up my body. Also I perceive my body among other bodies. I also perceive pain, pleasure, hunger, and satiation in my body. I perceive softness, heat, texture, light, sound. All of these things helps me to distinguish the sky, the earth, the seas, and all bodies from one another.

Now, it is not unreasonable to think that my ideas (objects of my sensory awareness) were caused by things quite distinct from my own thought, since my experience is (a) that these ideas were not controlled my me and (b) that these ideas gleaned from the senses were so very "lively and vivid.” In other words, my ideas were produced by bodies existing outside of me.

You might interject: what about the Dreaming Argument? The Deceiving God hypothesis? The possibility of an Evil Genius? How can I really know that my ideas gleaned from the senses were produced by material things?

We know what Descartes is going to say, don't we? He's learned a few things while meditating the past few days.

Again the question is this: Where do I get my ideas of sensible objects/material things? Three possible answers:

(a) myself,
(b) God or some other higher being,
(c) material things themselves.

Descartes rejects (a) and (b) as follows:

(a) doesn't work. For such ideas cannot originate from "my" mind, since the ideas in question are produced without my cooperation and often against my will. (Note: Descartes thinks unconscious perceiving thinking are absurd notions! Leibniz will challenge Descartes with regard to unconscious perceiving at least.)

(b) cannot be the answer. Ideas of external, material objects cannot be from God. I have such a strong conviction that my ideas of material things are produced by material things themselves, that if God or some other higher creature were in fact the cause of these ideas, then God would have to be a deceiver (especially since "the grasp of the senses is very obscure and confused").

Now, if neither (a) or (b), the answer must be (c)--material things themselves.

Real Distinction between Mind and Body

Here is how Descartes argues that mind and body are really distinct things:

1. I know that clear and distinct perception can be trusted.
2. So, for instance, the fact that I can clearly and distinctly understand one substance apart from another is enough to make certain that the two substances are really distinct, since they are capable of being separated, at least by God.
3. I have a clear and distinct understanding of my self (I am simply a thinking, non-extended substance).
4. I have a clear and distinct understanding of body (it is simply an extended, non-thinking substance).
Therefore
5.It is certain that I am really distinct from my body (any body) and can exist without it.

Let’s discuss objections to Descartes' view of the relation between mind and body. I will try to show how Descartes responds to these objections, with some speculation throw in for good measure.

For example, Descartes addresses the causal interaction between mind and body. It is a two-way street. The mind is not in control of the body the way that a sailor is in control of a ship. The union between mind and body is deeper. Discuss.

But how can the mind and body causally interact if minds are substances really distinct from bodies? How can an immaterial thing interact with a material thing, and conversely? Descartes posits that the brain is the interface between mind and body, and perhaps within the brain it is the pineal gland. (Only in the 1960s did scientists discover what purpose the pineal gland serves. Or at least one of its purposes: to produce melatonin. Though in the latest Gray’s Anatomy it says that it’s still unclear as to the pineal gland’s function.)

Descartes also argues elsewhere that we know that magnetism actually occurs. Oppositely charged particles attract. But really how does this work? We know
that
it works, but we really can’t explain
how
it does. Just as we know that the mind and body interact, but cannot fully explain it.
Descartes would respond: Haven't you, upon waking, ever been upset (at least for a moment)? For example, when you realize that it's not actually Christmas? Could you be this upset if you merely "experienced" the opening of gifts and "observed" the decorating of a Christmas tree?
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