Philosophy

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Introduction

René Descartes lived from 1596-1650 and was presented earlier in Unit 2. As

you may recall, he wrote his Meditations on First Philosophy in 1641.

Keep in mind that he lived in the context of the skepticism that was in fashion in

France in his time, for example, the works of Michel de Montaigne. Some scholars

refer to this period as the Age of Doubt.

The process of knowledge that had been described as “believe to know” in the

Medieval period (that belief in God would give certain knowledge) had changed

by Descartes’ lifetime into “doubt to know.” Descartes wanted to help arguments

about God, Soul (Mind), and External World. He was a man of strong faith, so

arguably his method of doubt is a bit of a ruse, to please the skeptics of his age. 

Descartes is facing old questions from the medieval period: How can we know

physical experiences are real? Does faith in God guarantee your knowledge will

be certain? Does God give knowledge only to the faithful?

One way to answer this is through a concept called the Manichean Universe, in which Good vs. Evil is locked in battle with

each other. Another way to answer it is through a concept called the Mechanical Universe. In this view, the universe is set

by God like a wound-up clock with multiple parts and gears, winding down.

Rationalism vs Empiricism

Did I already know that? This video is about Rationalism and Empiricism. Two concepts to do with Epistemology. The both deal with how we learn and both have there disadvantages and advantages. I will leave it up to you to decide which is better.

Rationalism Vs EmpiricismRationalism Vs Empiricism

Listen

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Direct Link - https://youtu.be/m1g8wjsEQyw

Direct Link - https://youtu.be/BrjYofKaVA4

Meditation I

Of The Things of Which We May Doubt

Descartes’ Method of Doubt is not really his own view. He is systematically doubting knowledge from senses, to strip

away any knowledge that can be doubted (he does what the skeptics do, rhetorically, to solve their problem.) In Descartes’

theory, we begin to see that “true” beliefs have to do with our own certainty.

Questions to Consider

As you read, consider the following questions:

Why does Descartes choose to take “doubts” seriously?

If you are thinking, do you have a guarantee that your thoughts are “real”? What about

physical objects?

Why does Descartes emphasize reason instead of senses like vision, touch, taste, etc.?

What is the difference between objects in the world like chairs, and objects like souls or

God?

Making Connections

Descartes’ discussion of doubt seems to have a commonality with Hume’s skepticism about having a direct impression of the self in Unit 2. Could Descartes claim that the self is a speci�c kind of idea? How would Plato describe Descartes’ method of doubt, and separating oneself from their senses?

Intro to Philosophy: Descartes' MeditationsIntro to Philosophy: Descartes' Meditations

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You read Meditation I in Unit 2. Use the link below if you would like to review it before moving on to Meditation II and III.

Descartes - Meditation I

Meditation II

Of The Nature of the Human Mind; and That it is More Easily Known than the Body 

 From  Meditations on First Philosophy. Edited by David B. Manley and Charles S. Taylor using John Veitch translation of

1901 

Introduction

To be deceived, one must exist: Even if we are being tricked by an evil genius or a vivid dream, it must be the case that we

do exist!

This gives Descartes one certain truth on which he can build all knowledge – I think therefore I am, Cogito Ergo Sum. 

This “I” is a thinking thing. If there are material things, their essential nature must be an extension (not thinking). This

extension is somehow grasped by the mind, rather than the senses. This means there is an essential difference between

Extension and Thinking.

Descartes’ wax example shows that even with variations of extension, we know it is still the same wax. We are thinking

things, the non-extended thinking substance grasping extended non-thinking substance.

Reading Assignment

1. The Meditation of yesterday has �lled my mind with so many doubts, that it is no longer in my power to forget them.

Nor do I see, meanwhile, any principle on which they can be resolved; and, just as if I had fallen all of a sudden into very

deep water, I am so greatly disconcerted as to be unable either to plant my feet �rmly on the bottom or sustain myself by

swimming on the surface. I will, nevertheless, make an effort, and try anew the same path on which I had entered

yesterday, that is, proceed by casting aside all that admits of the slightest doubt, not less than if I had discovered it to be

absolutely false; and I will continue always in this track until I shall �nd something that is certain, or at least, if I can do

nothing more, until I shall know with certainty that there is nothing certain. Archimedes, that he might transport the

entire globe from the place it occupied to another, demanded only a point that was �rm and immovable; so, also, I shall

been titled to entertain the highest expectations, if I am fortunate enough to discover only one thing that is certain and

indubitable.

2. I suppose, accordingly, that all the things which I see are false (�ctitious); I believe that none of those objects which my

fallacious memory represents ever existed; I suppose that I possess no senses; I believe that body, �gure, extension,

motion, and place are merely �ctions of my mind. What is there, then, that can be esteemed true? Perhaps this only, that

there is absolutely nothing certain.

3. But how do I know that there is not something different altogether from the objects I have now enumerated, of which it

is impossible to entertain the slightest doubt? Is there not a God, or some being, by whatever name I may designate him,

who causes these thoughts to arise in my mind? But why suppose such a being, for it may be I myself am capable of

producing them? Am I, then, at least not something? But I before denied that I possessed senses or a body; I hesitate,

however, for what follows from that? Am I so dependent on the body and the senses that without these I cannot exist? But

Check Your Answer

Descartes, in his quest for certainty in knowledge:

(a) Used a skeptical method of rejecting all thoughts harboring the slightest doubt.

(b) Used textbooks to prove his points.

(c) Used oral traditions to prove his points.

(d) Accepted as true all reasoning on mathematics.

The correct answer is (a) Used a skeptical method of rejecting all thoughts harboring the slightest doubt.

proceed by casting aside all that admits of the slightest doubt, not less than if I had discovered it to be absolutely

false;

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I had the persuasion that there was absolutely nothing in the world, that there was no sky and no earth, neither minds nor

bodies; was I not, therefore, at the same time, persuaded that I did not exist? Far from it; I assuredly existed, since I was

persuaded. But there is I know not what being, who is possessed at once of the highest power and the deepest cunning,

who is constantly employing all his ingenuity in deceiving me. Doubtless, then, I exist, since I am deceived; and, let him

deceive me as he may, he can never bring it about that I am nothing, so long as I shall be conscious that I am something. So

that it must, in �ne, be maintained, all things being maturely and carefully considered, that this proposition

(pronunciatum) I am, I exist, is necessarily true each time it is expressed by me, or conceived in my mind.

4. But I do not yet know with suf�cient clearness what I am, though assured that I am; and hence, in the next place, I must

take care, lest perchance I inconsiderately substitute some other object in room of what is properly myself, and thus

wander from truth, even in that knowledge ( cognition ) which I hold to be of all others the most certain and evident. For

this reason, I will now consider anew what I formerly believed myself to be, before I entered on the present train of

thought; and of my previous opinion I will retrench all that can in the least be invalidated by the grounds of doubt I have

adduced, in order that there may at length remain nothing but what is certain and indubitable.

5. What then did I formerly think I was? Undoubtedly I judged that I was a man. But what is a man? Shall I say a rational

animal? Assuredly not; for it would be necessary forthwith to inquire into what is meant by animal, and what by rational,

and thus, from a single question, I should insensibly glide into others, and these more dif�cult than the �rst; nor do I now

possess enough of leisure to warrant me in wasting my time amid subtleties of this sort. I prefer here to attend to the

thoughts that sprung up of themselves in my mind, and were inspired by my own nature alone, when I applied myself to

the consideration of what I was. In the �rst place, then, I thought that I possessed a countenance, hands, arms, and all the

fabric of members that appears in a corpse, and which I called by the name of body. It further occurred to me that I was

nourished, that I walked, perceived, and thought, and all those actions I referred to the soul; but what the soul itself was I

either did not stay to consider, or, if I did, I imagined that it was something extremely rare and subtle, like wind, or �ame,

or ether, spread through my grosser parts. As regarded the body, I did not even doubt of its nature, but thought I distinctly

knew it, and if I had wished to describe it according to the notions I then entertained, I should have explained myself in

this manner: By body I understand all that can be terminated by a certain �gure; that can be comprised in a certain place,

and so �ll a certain space as therefrom to exclude every other body; that can be perceived either by touch, sight, hearing,

taste, or smell; that can be moved in different ways, not indeed of itself, but by something foreign to it by which it is

touched [and from which it receives the impression]; for the power of self-motion, as likewise that of perceiving and

thinking, I held as by no means pertaining to the nature of body; on the contrary, I was somewhat astonished to �nd such

faculties existing in some bodies.

6. But [as to myself, what can I now say that I am], since I suppose there exists an extremely powerful, and, if I may so

speak, malignant being, whose whole endeavors are directed toward deceiving me? Can I af�rm that I possess any one of

all those attributes of which I have lately spoken as belonging to the nature of body? After attentively considering them in

my own mind, I �nd none of them that can properly be said to belong to myself. To recount them were idle and tedious. Let

us pass, then, to the attributes of the soul. The �rst mentioned were the powers of nutrition and walking; but, if it be true

that I have no body, it is true likewise that I am capable neither of walking nor of being nourished. Perception is another

attribute of the soul; but perception too is impossible without the body; besides, I have frequently, during sleep, believed

that I perceived objects which I afterward observed I did not in reality perceive. Thinking is another attribute of the soul;

and here I discover what properly belongs to myself. This alone is inseparable from me. I am I exist: this is certain; but how

often? As often as I think; for perhaps it would even happen, if I should wholly cease to think, that I should at the same

Check Your Answer

Descartes’ thought experiment of a “Cartesian Demon” seeking to deceive him is an attempt to produce:

(a) A good argument for knowledge.

(b) A strong argument that knowledge is possible.

(c) An unshakable case that knowledge is possible.

(d) A disturbing confusion.

The correct answer is (c) An unshakable case that knowledge is possible.

invalidated by the grounds of doubt I have adduced, in order that there may at length remain nothing but what is

certain and indubitable.

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time altogether cease to be. I now admit nothing that is not necessarily true. I am therefore, precisely speaking, only a

thinking thing, that is, a mind (mens siveanimus), understanding, or reason, terms whose signi�cation was before

unknown to me. I am, however, a real thing, and really existent; but what thing? The answer was, a thinking thing. 

7. The question now arises, am I aught besides? I will stimulate my imagination with a view to discover whether I am not

still something more than a thinking being. Now it is plain I am not the assemblage of members called the human body; I

am not a thin and penetrating air diffused through all these members, or wind, or �ame, or vapor, or breath, or any of all

the things I can imagine; for I supposed that all these were not, and, without changing the supposition, I �nd that I still feel

assured of my existence. But it is true, perhaps, that those very things which I suppose to be non-existent, because they

are unknown to me, are not in truth different from myself whom I know. This is a point I cannot determine, and do not now

enter into any dispute regarding it. I can only judge of things that are known to me: I am conscious that I exist, and I who

know that I exist inquire into what I am. It is, however, perfectly certain that the knowledge of my existence, thus precisely

taken, is not dependent on things, the existence of which is as yet unknown to me: and consequently it is not dependent

on any of the things I can feign in imagination. Moreover, the phrase itself, I frame an image (eff�ngo), reminds me of my

error; for I should in truth frame one if I were to imagine myself to be anything, since to imagine is nothing more than to

contemplate the �gure or image of a corporeal thing; but I already know that I exist, and that it is possible at the same

time that all those images, and in general all that relates to the nature of body, are merely dreams [or chimeras]. From this

I discover that it is not more reasonable to say, I will excite my imagination that I may know more distinctly what I am, than

to express myself as follows: I am now awake, and perceive something real; but because my perception is not suf�ciently

clear, I will of express purpose go to sleep that my dreams may represent to me the object of my perception with more

truth and clearness. And, therefore, I know that nothing of all that I can embrace in imagination belongs to the knowledge

which I have of myself, and that there is need to recall with the utmost care the mind from this mode of thinking, that it

may be able to know its own nature with perfect distinctness.

8. But what, then, am I? A thinking thing, it has been said. But what is a thinking thing? It is a thing that doubts,

understands, [conceives], af�rms, denies, wills, refuses; that imagines also, and perceives.

Check Your Answer

Descartes in his skeptical quest for certain knowledge imagines that his mind is affected by a:

(a) His internal imagination

(b) His emotional images

(c) An extremely powerful and malignant (evil) being seeking to deceive him

(d) An over active imagination that produces self-deception

The correct answer is (c) An extremely powerful and malignant (evil) being seeking to deceive him

But [as to myself, what can I now say that I am], since I suppose there exists an extremely powerful, and, if I may so

speak, malignant being, whose whole endeavors are directed toward deceiving me?

Check Your Answer

Descartes’ skeptical method of doubting his way to certainty in knowledge leads him to ask who or what he is, to

which he concludes that he is:

(a) Someone lost in the world

(b) Something he knows not what

(c) Someone who is �oundering

(d) Someone who is a thinking thing

The correct answer is (d) Someone who is a thinking thing

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9. Assuredly it is not little, if all these properties belong to my nature. But why should they not belong to it? Am I not that

very being who now doubts of almost everything; who, for all that, understands and conceives certain things; who af�rms

one alone as true, and denies the others; who desires to know more of them, and does not wish to be deceived; who

imagines many things, sometimes even despite his will; and is likewise percipient of many, as if through the medium of the

senses. Is there nothing of all this as true as that I am, even although I should be always dreaming, and although he who

gave me being employed all his ingenuity to deceive me? Is there also any one of these attributes that can be properly

distinguished from my thought, or that can be said to be separate from myself? For it is of itself so evident that it is I who

doubt, I who understand, and I who desire, that it is here unnecessary to add anything by way of rendering it more clear.

And I am as certainly the same being who imagines; for although it may be (as I before supposed) that nothing I imagine is

true, still the power of imagination does not cease really to exist in me and to form part of my thought. In �ne, I am the

same being who perceives, that is, who apprehends certain objects as by the organs of sense, since, in truth, I see light,

hear a noise, and feel heat. But it will be said that these presentations are false, and that I am dreaming. Let it be so. At all

events it is certain that I seem to see light, hear a noise, and feel heat; this cannot be false, and this is what in me is

properly called perceiving (sentire), which is nothing else than thinking.

10. From this I begin to know what I am with somewhat greater clearness and distinctness than heretofore. But,

nevertheless, it still seems to me, and I cannot help believing, that corporeal things, whose images are formed by thought

[which fall under the senses], and are examined by the same, are known with much greater distinctness than that I know

not what part of myself which is not imaginable; although, in truth, it may seem strange to say that I know and

comprehend with greater distinctness things whose existence appears to me doubtful, that are unknown, and do not

belong to me, than others of whose reality I am persuaded, that are known to me, and appertain to my proper nature; in a

word, than myself. But I see clearly what is the state of the case. My mind is apt to wander, and will not yet submit to be

restrained within the limits of truth. Let us therefore leave the mind to itself once more, and, according to it every kind of

liberty [permit it to consider the objects that appear to it from without], in order that, having afterward withdrawn it from

these gently and opportunely [ and �xed it on the consideration of its being and the properties it �nds in itself], it may then

be the more easily controlled.

11. Let us now accordingly consider the objects that are commonly thought to be [the most easily, and likewise] the most

distinctly known, viz, the bodies we touch and see; not, indeed, bodies in general, for these general notions are usually

somewhat more confused, but one body in particular. Take, for example, this piece of wax; it is quite fresh, having been but

recently taken from the beehive; it has not yet lost the sweetness of the honey it contained; it still retains somewhat of

the odor of the �owers from which it was gathered; its color, �gure, size, are apparent ( to the sight ); it is hard, cold, easily

handled; and sounds when struck upon with the �nger. In �ne, all that contributes to make a body as distinctly known as

possible, is found in the one before us. But, while I am speaking, let it be placed near the �re what remained of thetaste

exhales, the smell evaporates, the color changes, its �gure is destroyed, its size increases, it becomes liquid, it grows hot, it

can hardly be handled, and, although struck upon, it emits no sound. Does the same wax still remain after this change? It

must be admitted that it does remain; no one doubts it, or judges otherwise. What, then, was it I knew with so much

distinctness in the piece of wax? Assuredly, it could be nothing of all that I observed by means of the senses, since all the

things that fell under taste, smell, sight, touch, and hearing are changed, and yet the same wax remains.

12. It was perhaps what I now think, viz, that this wax was neither the sweetness of honey, the pleasant odor of �owers,

the whiteness, the �gure, nor the sound, but only a body that a little before appeared to me conspicuous under these

forms, and which is now perceived under others. But, to speak precisely, what is it that I imagine when I think of it in this

way? Let it be attentively considered, and, retrenching all that does not belong to the wax, let us see what remains. There

certainly remains nothing, except something extended, �exible, and movable. But what is meant by �exible and movable?

Is it not that I imagine that the piece of wax, being round, is capable of becoming square, or of passing from a square into a

triangular �gure? Assuredly such is not the case, because I conceive that it admits of an in�nity of similar changes; and I

am, moreover, unable to compass this in�nity by imagination, and consequently this conception which I have of the wax is

not the product of the faculty of imagination. But what now is this extension? Is it not also unknown ? for it becomes

greater when the wax is melted, greater when it is boiled, and greater still when the heat increases; and I should not

conceive [clearly and] according to truth, the wax as it is, if I did not suppose that the piece we are considering admitted

even of a wider variety of extension than I ever imagined, I must, therefore, admit that I cannot even comprehend by

imagination what the piece of wax is, and that it is the mind alone (mens, Lat., entendement, F.) which perceives it. I speak of

one piece in particular; for as to wax in general, this is still more evident. But what is the piece of wax that can be

perceived only by the [understanding or] mind? It is certainly the same which I see, touch, imagine; and, in �ne, it is the

same which, from the beginning, I believed it to be. But (and this it is of moment to observe)the perception of it is neither

an act of sight, of touch, nor of imagination, and never was either of these, though it might formerly seem so, but is simply

But what, then, am I ? A thinking thing, it has been said. But what is a thinking thing? It is a thing that doubts,

understands, [conceives], af�rms, denies, wills, refuses; that imagines also, and perceives.

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an intuition (inspectio) of the mind, which may be imperfect and confused, as it formerly was, or very clear and distinct, as

it is at present, according as the attention is more or less directed to the elements which it contains, and of which it is

composed.

13. But, meanwhile, I feel greatly astonished when I observe [the weakness of my mind, and] its proneness to error. For

although, without at all giving expression to what I think, I consider all this in my own mind, words yet occasionally impede

my progress, and I am almost led into error by the terms of ordinary language. We say, for example, that we see the same

wax when it is before us, and not that we judge it to be the same from its retaining the same color and �gure: whence I

should forthwith be disposed to conclude that the wax is known by the act of sight, and not by the intuition of the mind

alone, were it not for the analogous instance of human beings passing on in the street below, as observed from a window.

In this case I do not fail to say that I see the men themselves, just as I say that I see the wax; and yet what do I see from the

window beyond hats and cloaks that might cover arti�cial machines, whose motions might be determined by springs? But

I judge that there are human beings from these appearances, and thus I comprehend, by the faculty of judgment alone

which is in the mind, what I believed I saw with my eyes.

14. The man who makes it his aim to rise to knowledge superior to the common, ought to be ashamed to seek occasions of

doubting from the vulgar forms of speech: instead, therefore, of doing this, I shall proceed with the matter in hand, and

inquire whether I had a clearer and more perfect perception of the piece of wax when I �rst saw it, and when I thought I

knew it by means of the external sense itself, or, at all events, by the common sense (sensus communis), as it is called, that is,

by the imaginative faculty; or whether I rather apprehend it more clearly at present, after having examined with greater

care, both what it is, and in what way it can be known. It would certainly be ridiculous to entertain any doubt on this point.

For what, in that �rst perception, was there distinct? What did I perceive which any animal might not have perceived? But

when I distinguish the wax from its exterior forms, and when, as if I had stripped it of its vestments, I consider it quite

naked, it is certain, although some error may still be found in my judgment, that I cannot, nevertheless, thus apprehend it

without possessing a human mind.

15. But �nally, what shall I say of the mind itself, that is, of myself? for as yet I do not admit that I am anything but mind.

What, then! I who seem to possess so distinct an apprehension of the piece of wax, do I not know myself, both with

greater truth and certitude, and also much more distinctly and clearly? For ifI judge that the wax exists because I see it, it

assuredly follows, much more evidently, that I myself am or exist, for the same reason: for it is possible that what I see may

not in truth be wax, and that I do not even possess eyes with which to see anything; but it cannot be that when I see, or,

which comes to the same thing, when I think I see, I myself who think am nothing. So likewise, if I judge that the wax exists

because I touch it, it will still also follow that I am; and if I determine that my imagination, or any other cause, whatever it

be, persuades me of the existence of the wax, I will still draw the same conclusion. And what is here remarked of the piece

of wax, is applicable to all the other things that are external to me. And further, if the [notion or] perception of wax

appeared to me more precise and distinct, after that not only sight and touch, but many other causes besides, rendered it

manifest to my apprehension, with how much greater distinctness must I now know myself, since all the reasons that

contribute to the knowledge of the nature of wax, or of any body whatever, manifest still better the nature of my mind?

And there are besides so many other things in the mind itself that contribute to the illustration of its nature, that those

dependent on the body, to which I have here referred, scarcely merit to be taken into account.

16. But, in conclusion, I �nd I have insensibly reverted to the point I desired; for, since it is now manifest to me that bodies

themselves are not properly perceived by the senses nor by the faculty of imagination, but by the intellect alone; and since

they are not perceived because they are seen and touched, but only because they are understood [ or rightly

comprehended by thought ], I readily discover that there is nothing more easily or clearly apprehended than my own

Check Your Work

In expounding on the attributes of knowledge Descartes uses as the object of his discussion:

(a) Some wax fresh from a bee hive

(b) Some bottle brushes

(c) Nothing except pure thought

(d) Mathematical insights

The correct answer is (a) Some wax fresh from a bee hive

Take, for example, this piece of wax; it is quite fresh, having been but recently taken from the beehive; it has not yet

lost the sweetness of the honey it contained;

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mind. But because it is dif�cult to rid one's self so promptly of an opinion to which one has been long accustomed, it will be

desirable to tarry for some time at this stage, that, by long continued meditation, I may more deeply impress upon my

memory this new knowledge.

Meditation III

Of God: That He Exists

From Descartes's Meditations on First Philosophy. Edited by David B. Manley and Charles S. Taylor using John Veitch translation of

1901

Introduction

Descartes develops a general criterion for truth: All things perceived clearly and distinctly are true. In the third

meditation, he extends this concept to the idea of God.

Existence of God: 

Descartes’ mind contains an idea of an in�nite being

Descartes is only �nite, so the idea of an in�nite being cannot have come from his �nite mind

So God, the in�nite being, must have given him this in�nite idea of God (as only an in�nite being could create an

in�nite idea)

So God must exist!

The key idea is that premise 3 assumes what the conclusion needed to prove, so the argument is circular or an example of

begging the question.

Reading Assignment

1. I WILL now close my eyes, I will stop my ears, I will turn away my senses from their objects, I will even efface from my

consciousness all the images of corporeal things; or at least, because this can hardly be accomplished, I will consider them

as empty and false; and thus, holding converse only with myself, and closely examining my nature, I will endeavor to obtain

by degrees a more intimate and familiar knowledge of myself. I am a thinking ( conscious ) thing, that is, a being who

doubts, af�rms, denies, knows a few objects, and is ignorant of many,-- who loves, hates], wills, refuses, who imagines

likewise, and perceives; for, as I before remarked, although the things which I perceive or imagine are perhaps nothing at

all apart from me and in themselves], I am nevertheless assured that those modes of consciousness which I call

perceptions and imaginations, in as far only as they are modes of consciousness, exist in me.

2. And in the little I have said I think I have summed up all that I really know, or at least all that up to this time I was aware I

knew. Now, as I am endeavoring to extend my knowledge more widely, I will use circumspection, and consider with care

whether I can still discover in myself anything further which I have not yet hitherto observed. I am certain that I am a

thinking thing; but do I not therefore likewise know what is required to render me certain of a truth? In this �rst

knowledge, doubtless, there is nothing that gives me assurance of its truth except the clear and distinct perception of

what I af�rm, which would not indeed be suf�cient to give me the assurance that what I say is true, if it could ever happen

that anything I thus clearly and distinctly perceived should prove false; and accordingly it seems to me that I may now take

as a general rule, that all that is very clearly and distinctly apprehended (conceived) is true.

3. Nevertheless I before received and admitted many things as wholly certain and manifest, which yet I afterward found

to be doubtful. What, then, were those? They were the earth, the sky, the stars, and all the other objects which I was in the

habit of perceiving by the senses. But what was it that I clearly and distinctly] perceived in them? Nothing more than that

the ideas and the thoughts of those objects were presented to my mind. And even now I do not deny that these ideas are

found in my mind. But there was yet another thing which I af�rmed, and which, from having been accustomed to believe it,

I thought I clearly perceived, although, in truth, I did not perceive it at all; I mean the existence of objects external to me,

from which those ideas proceeded, and to which they had a perfect resemblance; and it was here I was mistaken, or if I

judged correctly, this assuredly was not to be traced to any knowledge I possessed (the force of my perception, Lat.).

4. But when I considered any matter in arithmetic and geometry, that was very simple and easy, as, for example, that two

and three added together make �ve, and things of this sort, did I not view them with at least suf�cient clearness to

warrant me in af�rming their truth? Indeed, if I afterward judged that we ought to doubt of these things, it was for no

other reason than because it occurred to me that a God might perhaps have given me such a nature as that I should be

deceived, even respecting the matters that appeared to me the most evidently true. But as often as this preconceived

opinion of the sovereign power of a God presents itself to my mind, I am constrained to admit that it is easy for him, if he

wishes it, to cause me to err, even in matters where I think I possess the highest evidence; and, on the other hand, as often

as I direct my attention to things which I think I apprehend with great clearness, I am so persuaded of their truth that I

naturally break out into expressions such as these: Deceive me who may, no one will yet ever be able to bring it about that

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I am not, so long as I shall be conscious that I am, or at any future time cause it to be true that I have never been, it being

now true that I am, or make two and three more or less than �ve, in supposing which, and other like absurdities, I discover

a manifest contradiction. And in truth, as I have no ground for believing that Deity is deceitful, and as, indeed, I have not

even considered the reasons by which the existence of a Deity of any kind is established, the ground of doubt that rests

only on this supposition is very slight, and, so to speak, metaphysical. But, that I may be able wholly to remove it, I must

inquire whether there is a God, as soon as an opportunity of doing so shall present itself; and if I �nd that there is a God, I

must examine likewise whether he can be a deceiver; for, without the knowledge of these two truths, I do not see that I

can ever be certain of anything. And that I may be enabled to examine this without interrupting the order of meditation I

have proposed to myself which is, to pass by degrees from the notions that I shall �nd �rst in my mind to those I shall

afterward discover in it], it is necessary at this stage to divide all my thoughts into certain classes, and to consider in which

of these classes truth and error are, strictly speaking, to be found.

5. Of my thoughts some are, as it were, images of things, and to these alone properly belongs the name IDEA; as when I

think represent to my mind ] a man, a chimera, the sky, an angel or God. Others, again, have certain other forms; as when I

will, fear, af�rm, or deny, I always, indeed, apprehend something as the object of my thought, but I also embrace in thought

something more than the representation of the object; and of this class of thoughts some are called volitions or affections,

and others judgments.

6. Now, with respect to ideas, if these are considered only in themselves, and are not referred to any object beyond them,

they cannot, properly speaking, be false; for, whether I imagine a goat or chimera, it is not less true that I imagine the one

than the other. Nor need we fear that falsity may exist in the will or affections; for, although I may desire objects that are

wrong, and even that never existed, it is still true that I desire them. There thus only remain our judgments, in which we

must take diligent heed that we be not deceived. But the chief and most ordinary error that arises in them consists in

judging that the ideas which are in us are like or conformed to the things that are external to us; for assuredly, if we but

considered the ideas themselves as certain modes of our thought (consciousness), without referring them to anything

beyond, they would hardly afford any occasion of error.

7. But among these ideas, some appear to me to be innate, others adventitious, and others to be made by myself

(factitious); for, as I have the power of conceiving what is called a thing, or a truth, or a thought, it seems to me that I hold

this power from no other source than my own nature; but if I now hear a noise, if I see the sun, or if I feel heat, I have all

along judged that these sensations proceeded from certain objects existing out of myself; and, in �ne, it appears to me

that sirens, hippogryphs, and the like, are inventions of my own mind. But I may even perhaps come to be of opinion that

all my ideas are of the class which I call adventitious, or that they are all innate, or that they are all factitious; for I have not

yet clearly discovered their true origin.

8. What I have here principally to do is to consider, with reference to those that appear to come from certain objects

without me, what grounds there are for thinking them like these objects. The �rst of these grounds is that it seems to me I

am so taught by nature; and the second that I am conscious that those ideas are not dependent on my will, and therefore

not on myself, for they are frequently presented to me against my will, as at present, whether I will or not, I feel heat; and I

am thus persuaded that this sensation or idea (sensum vel ideam) of heat is produced in me by something different from

myself, viz., by the heat of the �re by which I sit. And it is very reasonable to suppose that this object impresses me with its

own likeness rather than any other thing.

9. But I must consider whether these reasons are suf�ciently strong and convincing. When I speak of being taught by

nature in this matter, I understand by the word nature only a certain spontaneous impetus that impels me to believe in a

resemblance between ideas and their objects, and not a natural light that affords a knowledge of its truth. But these two

things are widely different; for what the natural light shows to be true can be in no degree doubtful, as, for example, that I

am because I doubt, and other truths of the like kind; inasmuch as I possess no other faculty whereby to distinguish truth

from error, which can teach me the falsity of what the natural light declares to be true, and which is equally trustworthy;

but with respect to seemingly] natural impulses, I have observed, when the question related to the choice of right or

wrong in action, that they frequently led me to take the worse part; nor do I see that I have any better ground for

following them in what relates to truth and error.

10. Then, with respect to the other reason, which is that because these ideas do not depend on my will, they must arise

from objects existing without me, I do not �nd it more convincing than the former, for just as those natural impulses, of

which I have lately spoken, are found in me, notwithstanding that they are not always in harmony with my will, so likewise

it may be that I possess some power not suf�ciently known to myself capable of producing ideas without the aid of

external objects, and, indeed, it has always hitherto appeared to me that they are formed during sleep, by some power of

this nature, without the aid of aught external.

11. And, in �ne, although I should grant that they proceeded from those objects, it is not a necessary consequence that

they must be like them. On the contrary, I have observed, in a number of instances, that there was a great difference

between the object and its idea. Thus, for example, I �nd in my mind two wholly diverse ideas of the sun; the one, by which

it appears to me extremely small draws its origin from the senses, and should be placed in the class of adventitious ideas;

the other, by which it seems to be many times larger than the whole earth, is taken up on astronomical grounds, that is,

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elicited from certain notions born with me, or is framed by myself in some other manner. These two ideas cannot certainly

both resemble the same sun; and reason teaches me that the one which seems to have immediately emanated from it is

the most unlike.

12. And these things suf�ciently prove that hitherto it has not been from a certain and deliberate judgment, but only from

a sort of blind impulse, that I believed existence of certain things different from myself, which, by the organs of sense, or

by whatever other means it might be, conveyed their ideas or images into my mind and impressed it with their likenesses].

13. But there is still another way of inquiring whether, of the objects whose ideas are in my mind, there are any that exist

out of me. If ideas are taken in so far only as they are certain modes of consciousness, I do not remark any difference or

inequality among them, and all seem, in the same manner, to proceed from myself; but, considering them as images, of

which one represents one thing and another a different, it is evident that a great diversity obtains among them. For,

without doubt, those that represent substances are something more, and contain in themselves, so to speak, more

objective reality that is, participate by representation in higher degrees of being or perfection], than those that represent

only modes or accidents; and again, the idea by which I conceive a God sovereign], eternal, in�nite, immutable], all-

knowing, all-powerful, and the creator of all things that are out of himself, this, I say, has certainly in it more objective

reality than those ideas by which �nite substances are represented.

14. Now, it is manifest by the natural light that there must at least be as much reality in the ef�cient and total cause as in

its effect; for whence can the effect draw its reality if not from its cause? And how could the cause communicate to it this

reality unless it possessed it in itself? And hence it follows, not only that what is cannot be produced by what is not, but

likewise that the more perfect, in other words, that which contains in itself more reality, cannot be the effect of the less

perfect; and this is not only evidently true of those effects, whose reality is actual or formal, but likewise of ideas, whose

reality is only considered as objective. Thus, for example, the stone that is not yet in existence, not only cannot now

commence to be, unless it be produced by that which possesses in itself, formally or eminently, all that enters into its

composition, in other words, by that which contains in itself the same properties that are in the stone, or others superior

to them]; and heat can only be produced in a subject that was before devoid of it, by a cause that is of an order, degree or

kind], at least as perfect as heat; and so of the others. But further, even the idea of the heat, or of the stone, cannot exist in

me unless it be put there by a cause that contains, at least, as much reality as I conceive existent in the heat or in the stone

for although that cause may not transmit into my idea anything of its actual or formal reality, we ought not on this account

to imagine that it is less real; but we ought to consider that, as every idea is a work of the mind], its nature is such as of

itself to demand no other formal reality than that which it borrows from our consciousness, of which it is but a mode that

is, a manner or way of thinking]. But in order that an idea may contain this objective reality rather than that, it must

doubtless derive it from some cause in which is found at least as much formal reality as the idea contains of objective; for,

if we suppose that there is found in an idea anything which was not in its cause, it must of course derive this from nothing.

But, however imperfect may be the mode of existence by which a thing is objectively or by representation] in the

understanding by its idea, we certainly cannot, for all that, allege that this mode of existence is nothing, nor, consequently,

that the idea owes its origin to nothing.

15. Nor must it be imagined that, since the reality which considered in these ideas is only objective, the same reality need

not be formally (actually) in the causes of these ideas, but only objectively: for, just as the mode of existing objectively

belongs to ideas by their peculiar nature, so likewise the mode of existing formally appertains to the causes of these ideas

(at least to the �rst and principal), by their peculiar nature. And although an idea may give rise to another idea, this regress

cannot, nevertheless, be in�nite; we must in the end reach a �rst idea, the cause of which is, as it were, the archetype in

which all the reality or perfection] that is found objectively or by representation] in these ideas is contained formally and

in act]. I am thus clearly taught by the natural light that ideas exist in me as pictures or images, which may, in truth, readily

fall short of the perfection of the objects from which they are taken, but can never contain anything greater or more

perfect.

16. And in proportion to the time and care with which I examine all those matters, the conviction of their truth brightens

and becomes distinct. But, to sum up, what conclusion shall I draw from it all? It is this: if the objective reality or

perfection] of any one of my ideas be such as clearly to convince me, that this same reality exists in me neither formally

nor eminently, and if, as follows from this, I myself cannot be the cause of it, it is a necessary consequence that I am not

alone in the world, but that there is besides myself some other being who exists as the cause of that idea; while, on the

contrary, if no such idea be found in my mind, I shall have no suf�cient ground of assurance of the existence of any other

being besides myself, for, after a most careful search, I have, up to this moment, been unable to discover any other ground.

17. But, among these my ideas, besides that which represents myself, respecting which there can be here no dif�culty,

there is one that represents a God; others that represent corporeal and inanimate things; others angels; others animals;

and, �nally, there are some that represent men like myself.

18. But with respect to the ideas that represent other men, or animals, or angels, I can easily suppose that they were

formed by the mingling and composition of the other ideas which I have of myself, of corporeal things, and of God,

although they were, apart from myself, neither men, animals, nor angels.

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19. And with regard to the ideas of corporeal objects, I never discovered in them anything so great or excellent which I

myself did not appear capable of originating; for, by considering these ideas closely and scrutinizing them individually, in

the same way that I yesterday examined the idea of wax, I �nd that there is but little in them that is clearly and distinctly

perceived. As belonging to the class of things that are clearly apprehended, I recognize the following, viz, magnitude or

extension in length, breadth, and depth; �gure, which results from the termination of extension; situation, which bodies of

diverse �gures preserve with reference to each other; and motion or the change of situation; to which may be added

substance, duration, and number. But with regard to light, colors, sounds, odors, tastes, heat, cold, and the other tactile

qualities, they are thought with so much obscurity and confusion, that I cannot determine even whether they are true or

false; in other words, whether or not the ideas I have of these qualities are in truth the ideas of real objects. For although I

before remarked that it is only in judgments that formal falsity, or falsity properly so called, can be met with, there may

nevertheless be found in ideas a certain material falsity, which arises when they represent what is nothing as if it were

something. Thus, for example, the ideas I have of cold and heat are so far from being clear and distinct, that I am unable

from them to discover whether cold is only the privation of heat, or heat the privation of cold; or whether they are or are

not real qualities: and since, ideas being as it were images there can be none that does not seem to us to represent some

object, the idea which represents cold as something real and positive will not improperly be called false, if it be correct to

say that cold is nothing but a privation of heat; and so in other cases.

20. To ideas of this kind, indeed, it is not necessary that I should assign any author besides myself: for if they are false, that

is, represent objects that are unreal, the natural light teaches me that they proceed from nothing; in other words, that

they are in me only because something is wanting to the perfection of my nature; but if these ideas are true, yet because

they exhibit to me so little reality that I cannot even distinguish the object represented from nonbeing, I do not see why I

should not be the author of them.

21. With reference to those ideas of corporeal things that are clear and distinct, there are some which, as appears to me,

might have been taken from the idea I have of myself, as those of substance, duration, number, and the like. For when I

think that a stone is a substance, or a thing capable of existing of itself, and that I am likewise a substance, although I

conceive that I am a thinking and non-extended thing, and that the stone, on the contrary, is extended and unconscious,

there being thus the greatest diversity between the two concepts, yet these two ideas seem to have this in common that

they both represent substances. In the same way, when I think of myself as now existing, and recollect besides that I

existed some time ago, and when I am conscious of various thoughts whose number I know, I then acquire the ideas of

duration and number, which I can afterward transfer to as many objects as I please. With respect to the other qualities

that go to make up the ideas of corporeal objects, viz, extension, �gure, situation, and motion, it is true that they are not

formally in me, since I am merely a thinking being; but because they are only certain modes of substance, and because I

myself am a substance, it seems possible that they may be contained in me eminently.

22. There only remains, therefore, the idea of God, in which I must consider whether there is anything that cannot be

supposed to originate with myself. By the name God, I understand a substance in�nite, eternal, immutable], independent,

all-knowing, all-powerful, and by which I myself, and every other thing that exists, if any such there be, were created. But

these properties are so great and excellent, that the more attentively I consider them the less I feel persuaded that the

idea I have of them owes its origin to myself alone. And thus it is absolutely necessary to conclude, from all that I have

before said, that God exists.

23. For though the idea of substance be in my mind owing to this, that I myself am a substance, I should not, however, have

the idea of an in�nite substance, seeing I am a �nite being, unless it were given me by some substance in reality in�nite.

24. And I must not imagine that I do not apprehend the in�nite by a true idea, but only by the negation of the �nite, in the

same way that I comprehend repose and darkness by the negation of motion and light: since, on the contrary, I clearly

perceive that there is more reality in the in�nite substance than in the �nite, and therefore that in some way I possess the

perception (notion) of the in�nite before that of the �nite, that is, the perception of God before that of myself, for how

could I know that I doubt, desire, or that something is wanting to me, and that I am not wholly perfect, if I possessed no

idea of a being more perfect than myself, by comparison of which I knew the de�ciencies of my nature?

25. And it cannot be said that this idea of God is perhaps materially false, and consequently that it may have arisen from

nothing in other words, that it may exist in me from my imperfections as I before said of the ideas of heat and cold, and the

like: for, on the contrary, as this idea is very clear and distinct, and contains in itself more objective reality than any other,

there can be no one of itself more true, or less open to the suspicion of falsity. The idea, I say, of a being supremely perfect,

and in�nite, is in the highest degree true; for although, perhaps, we may imagine that such a being does not exist, we

cannot, nevertheless, suppose that his idea represents nothing real, as I have already said of the idea of cold. It is likewise

clear and distinct in the highest degree, since whatever the mind clearly and distinctly conceives as real or true, and as

implying any perfection, is contained entire in this idea. And this is true, nevertheless, although I do not comprehend the

in�nite, and although there may be in God an in�nity of things that I cannot comprehend, nor perhaps even compass by

thought in any way; for it is of the nature of the in�nite that it should not be comprehended by the �nite; and it is enough

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that I rightly understand this, and judge that all which I clearly perceive, and in which I know there is some perfection, and

perhaps also an in�nity of properties of which I am ignorant, are formally or eminently in God, in order that the idea I have

of him may be come the most true, clear, and distinct of all the ideas in my mind.

26. But perhaps I am something more than I suppose myself to be, and it may be that all those perfections which I

attribute to God, in some way exist potentially in me, although they do not yet show themselves, and are not reduced to

act. Indeed, I am already conscious that my knowledge is being increased and perfected] by degrees; and I see nothing to

prevent it from thus gradually increasing to in�nity, nor any reason why, after such increase and perfection, I should not

be able thereby to acquire all the other perfections of the Divine nature; nor, in �ne, why the power I possess of acquiring

those perfections, if it really now exist in me, should not be suf�cient to produce the ideas of them.

27. Yet, on looking more closely into the matter, I discover that this cannot be; for, in the �rst place, although it were true

that my knowledge daily acquired new degrees of perfection, and although there were potentially in my nature much that

was not as yet actually in it, still all these excellences make not the slightest approach to the idea I have of the Deity, in

whom there is no perfection merely potentially but all actually] existent; for it is even an unmistakable token of

imperfection in my knowledge, that it is augmented by degrees. Further, although my knowledge increase more and more,

nevertheless I am not, therefore, induced to think that it will ever be actually in�nite, since it can never reach that point

beyond which it shall be incapable of further increase. But I conceive God as actually in�nite, so that nothing can be added

to his perfection. And, in �ne, I readily perceive that the objective being of an idea cannot be produced by a being that is

merely potentially existent, which, properly speaking, is nothing, but only by a being existing formally or actually.

28. And, truly, I see nothing in all that I have now said which it is not easy for any one, who shall carefully consider it, to

discern by the natural light; but when I allow my attention in some degree to relax, the vision of my mind being obscured,

and, as it were, blinded by the images of sensible objects, I do not readily remember the reason why the idea of a being

more perfect than myself, must of necessity have proceeded from a being in reality more perfect. On this account I am

here desirous to inquire further, whether I, who possess this idea of God, could exist supposing there were no God.

29. And I ask, from whom could I, in that case, derive my existence? Perhaps from myself, or from my parents, or from

some other causes less perfect than God; for anything more perfect, or even equal to God, cannot be thought or imagined.

30. But if I were independent of every other existence, and] were myself the author of my being, I should doubt of nothing,

I should desire nothing, and, in �ne, no perfection would be awanting to me; for I should have bestowed upon myself every

perfection of which I possess the idea, and I should thus be God. And it must not be imagined that what is now wanting to

me is perhaps of more dif�cult acquisition than that of which I am already possessed; for, on the contrary, it is quite

manifest that it was a matter of much higher dif�culty that I, a thinking being, should arise from nothing, than it would be

for me to acquire the knowledge of many things of which I am ignorant, and which are merely the accidents of a thinking

substance; and certainly, if I possessed of myself the greater perfection of which I have now spoken in other words, if I

were the author of my own existence], I would not at least have denied to myself things that may be more easily obtained

as that in�nite variety of knowledge of which I am at present destitute]. I could not, indeed, have denied to myself any

property which I perceive is contained in the idea of God, because there is none of these that seems to me to be more

dif�cult to make or acquire; and if there were any that should happen to be more dif�cult to acquire, they would certainly

appear so to me (supposing that I myself were the source of the other things I possess), because I should discover in them

a limit to my power.

31. And though I were to suppose that I always was as I now am, I should not, on this ground, escape the force of these

reasonings, since it would not follow, even on this supposition, that no author of my existence needed to be sought after.

For the whole time of my life may be divided into an in�nity of parts, each of which is in no way dependent on any other;

and, accordingly, because I was in existence a short time ago, it does not follow that I must now exist, unless in this

moment some cause create me anew as it were, that is, conserve me. In truth, it is perfectly clear and evident to all who

will attentively consider the nature of duration, that the conservation of a substance, in each moment of its duration,

requires the same power and act that would be necessary to create it, supposing it were not yet in existence; so that it is

manifestly a dictate of the natural light that conservation and creation differ merely in respect of our mode of thinking

and not in reality].

32. All that is here required, therefore, is that I interrogate myself to discover whether I possess any power by means of

which I can bring it about that I, who now am, shall exist a moment afterward: for, since I am merely a thinking thing (or

since, at least, the precise question, in the meantime, is only of that part of myself ), if such a power resided in me, I should,

without doubt, be conscious of it; but I am conscious of no such power, and thereby I manifestly know that I am dependent

upon some being different from myself.

33. But perhaps the being upon whom I am dependent is not God, and I have been produced either by my parents, or by

some causes less perfect than Deity. This cannot be: for, as I before said, it is perfectly evident that there must at least be

as much reality in the cause as in its effect; and accordingly, since I am a thinking thing and possess in myself an idea of

God, whatever in the end be the cause of my existence, it must of necessity be admitted that it is likewise a thinking being,

and that it possesses in itself the idea and all the perfections I attribute to Deity. Then it may again be inquired whether

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this cause owes its origin and existence to itself, or to some other cause. For if it be self-existent, it follows, from what I

have before laid down, that this cause is God; for, since it possesses the perfection of self-existence, it must likewise,

without doubt, have the power of actually possessing every perfection of which it has the idea--in other words, all the

perfections I conceive to belong to God. But if it owe its existence to another cause than itself, we demand again, for a

similar reason, whether this second cause exists of itself or through some other, until, from stage to stage, we at length

arrive at an ultimate cause, which will be God.

34. And it is quite manifest that in this matter there can be no in�nite regress of causes, seeing that the question raised

respects not so much the cause which once produced me, as that by which I am at this present moment conserved.

35. Nor can it be supposed that several causes concurred in my production, and that from one I received the idea of one of

the perfections I attribute to Deity, and from another the idea of some other, and thus that all those perfections are

indeed found somewhere in the, but do not all exist together in a single being who is God; for, on the contrary, the unity,

the simplicity, or inseparability of all the properties of Deity, is one of the chief perfections I conceive him to possess; and

the idea of this unity of all the perfections of Deity could certainly not be put into my mind by any cause from which I did

not likewise receive the ideas of all the other perfections; for no power could enable me to embrace them in an

inseparable unity, without at the same time giving me the knowledge of what they were and of their existence in a

particular mode].

36. Finally, with regard to my parents from whom it appears I sprung ], although all that I believed respecting them be

true, it does not, nevertheless, follow that I am conserved by them, or even that I was produced by them, in so far as I am a

thinking being. All that, at the most, they contributed to my origin was the giving of certain dispositions ( modi�cations ) to

the matter in which I have hitherto judged that I or my mind, which is what alone I now consider to be myself, is inclosed;

and thus there can here be no dif�culty with respect to them, and it is absolutely necessary to conclude from this alone

that I am, and possess the idea of a being absolutely perfect, that is, of God, that his existence is most clearly

demonstrated.

37. There remains only the inquiry as to the way in which I received this idea from God; for I have not drawn it from the

senses, nor is it even presented to me unexpectedly, as is usual with the ideas of sensible objects, when these are

presented or appear to be presented to the external organs of the senses; it is not even a pure production or �ction of my

mind, for it is not in my power to take from or add to it; and consequently there but remains the alternative that it is

innate, in the same way as is the idea of myself.

38. And, in truth, it is not to be wondered at that God, at my creation, implanted this idea in me, that it might serve, as it

were, for the mark of the workman impressed on his work; and it is not also necessary that the mark should be something

different from the work itself; but considering only that God is my creator, it is highly probable that he in some way

fashioned me after his own image and likeness, and that I perceive this likeness, in which is contained the idea of God, by

the same faculty by which I apprehend myself, in other words, when I make myself the object of re�ection, I not only �nd

that I am an incomplete, imperfect] and dependent being, and one who unceasingly aspires after something better and

greater than he is; but, at the same time, I am assured likewise that he upon whom I am dependent possesses in himself all

the goods after which I aspire and the ideas of which I �nd in my mind], and that not merely inde�nitely and potentially,

but in�nitely and actually, and that he is thus God. And the whole force of the argument of which I have here availed

myself to establish the existence of God, consists in this, that I perceive I could not possibly be of such a nature as I am,

and yet have in my mind the idea of a God, if God did not in reality exist--this same God, I say, whose idea is in my mind--

that is, a being who possesses all those lofty perfections, of which the mind may have some slight conception, without,

however, being able fully to comprehend them, and who is wholly superior to all defect and has nothing that marks

imperfection]: whence it is suf�ciently manifest that he cannot be a deceiver, since it is a dictate of the natural light that all

fraud and deception spring from some defect. 39. But before I examine this with more attention, and pass on to the

consideration of other truths that may be evolved out of it, I think it proper to remain here for some time in the

contemplation of God himself--that I may ponder at leisure his marvelous attributes--and behold, admire, and adore the

beauty of this light so unspeakably great, as far, at least, as the strength of my mind, which is to some degree dazzled by

the sight, will permit. For just as we learn by faith that the supreme felicity of another life consists in the contemplation of

the Divine majesty alone, so even now we learn from experience that a like meditation, though incomparably less perfect,

is the source of the highest satisfaction of which we are susceptible in this life.

Acknowledging the Skeptics

The Evil Demon and the Brain in the Vat

When Descartes acknowledges doubts about the existence of the external world, he gives two reasons to doubt:

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there may be an evil demon or evil genius deceiving us (a modern-day version is John Pollock's "A Brain in a

Vat" scenario)

This experience may be a vivid dream

Descartes is not a skeptic, he is using it as a strategy. In the �rst two Meditations, Descartes uses skeptical doubt as

a tool to sort through and assess his beliefs. Descartes recognizes that he, like other people, must have some false

beliefs mixed among his true ones. Just as one might sort apples and toss out the ones that have gone bad,

Descartes hopes to sort out his beliefs to discover which ones are both justi�ed and true, and which ones are either

unjusti�ed or false.

At the end of the First Meditation, Descartes introduces the possibility that there is a "powerful, cunning demon"

whose sole aim is to deceive Descartes into accepting things that are false. Descartes's evil demon serves the same

function as John Pollack's brain in a vat scenario. Descartes does not believe that there really is a demon who

deceives him, just as you do not believe that you are really a brain in a vat (we hope!). But like the brain in the vat

hypothesis, the evil demon hypothesis helps Descartes sort his beliefs into two categories: those that can be

doubted, and those (if any) that are self-evidently true. Descartes identi�es the beliefs in this latter category as

those that are apprehended (perceived, cognized) so clearly and distinctly that they cannot be doubted.

Descartes's argument is an effort to escape skepticism and prove once and for all that skepticism is false. But

Descartes begins by giving skeptical doubt its due. He considers different categories of his beliefs, and asks himself

"Is it possible for me to doubt that this is true?" If the answer is "yes," then the belief in question cannot be self-

evidently true: According to Descartes, a belief is self-evident only if it is indubitable, that is, only if we cannot

sensibly doubt it - Descartes applies the acid of skeptical doubt to different categories of beliefs. By considering

that he might be dreaming, he �nds that he can doubt any beliefs that he gained with the use of his senses. This

brings into doubt scienti�c beliefs as well as our everyday beliefs about the things and people around us: Descartes

says, in effect, "In the past, I have had dreams that seemed so real that they deceived me: I didn't realize that I was

dreaming until I woke. What proof do I now have that can show me for certain that I'm not asleep?"

Descartes does not believe that there is a "malicious, powerful, cunning demon" who tries to deceive him. But he

thinks that this situation is imaginable, conceivable and that this possibility justi�es doubts about all sorts of things.

Three Types of Ideas in Descartes's Theory

Descartes’ theory includes three different types of ideas:

Adventitious (outside source, physical objects, for example, a chair)

Fictitious (made up, make-believe, hippogryph; these are often recombinations of familiar items we already

knew as adventitious ideas – for example, in Star Wars, the name of Chewbacca comes from chewing tobacco)

Innate (God)

Ideas can be known through the natural light of reason; we clearly and distinctly perceive adventitious ideas, and

we use our reason to know innate ideas like God.

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Descartes:  A Casual Argument for the Existence of God

Descartes wanted to �nd an adequate response to the skeptic. He hoped that his effort to clean up his belief system

would enable him to show once and for all that we have justi�ed beliefs. Descartes thought that to show this he had

to prove that God exists, and he thought that he needed to prove that God's existence can be demonstrated simply

by self-evident propositions. In Meditation V (not assigned here), Descartes offers a version of the Ontological

argument, which you may have encountered in Unit 3. But in Meditation III, he offers a causal argument for the

existence of God. Here is one reading of Descartes' argument:

My idea of God is objectively perfect.

If an idea is objectively perfect, then the cause of that idea must be a perfect being.

Hence, God exists

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According to Descartes, this argument is like the Cogito argument: once you understand the argument, it is

impossible to doubt that the proposition "God exists" is true. Descartes regards premise two as clearly and

distinctly true. He thinks it is a self-evident principle of causation. And premise one can be taken simply as a

de�nition of God. Perhaps, Descartes could have relied on a weaker premise, like the one Anselm employs in the

Ontological Argument (discussed previously): the premise, "We have an idea of a perfect being."

The Cartesian Circle

Some philosophers have argued that Descartes' causal argument for God's existence is circular: It relies on

Descartes' claim that clear and distinct ideas are veridical.

Veridicality of Clear and Distinct Ideas: "Whenever I clearly and distinctly perceive that a proposition is

true, it must be true."

What reason can we have for believing this claim? Later, Descartes argues that this claim must be true because

otherwise, God would be a deceiver. But God's being a deceiver is inconsistent with the claim that God is perfect,

and according to Descartes, we have a clear and distinct perception that God is perfect. Since this perception is

clear and distinct, it must be true that God is perfect.

Do you see why this argument is circular? It relies on the veridicality of clear and distinct ideas to justify the claim

that God is perfect but then relies on the claim that God is perfect to justify the belief that clear and distinct ideas

must be true.

Categories of Philosophers 

How Do We Know?

What Do We Have Knowledge Of?

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Think About It

Is Descartes' argument circular? Does it help that Descartes offers an alternative argument in favor of God's existence later, in Meditation V?

Rationalist  we know using reason, thinking,

understanding, powers of the mind

Empiricist we know using our senses, physical

experience, taste, touch, sight, etc.

Idealist we have knowledge of ideas, concepts,

usually in mind 

Materialist we have knowledge of matter, some

substance outside of our minds

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Both Descartes and Plato are rationalist and idealist. We get to know ideas through thinking, reason, re�ecting gaining

understanding using the mind, and these ideas can be categorized into sets and types (Plato’s Divided Line, Descartes’

three types of ideas from the Meditations).

One added note about Descartes: for many philosophers, it is a bit arti�cial to call him an idealist. He really believes that

once he gives the categories of ideas (innate, adventitious, and �ctitious) that he has then "saved" the reality of physical

matter as well. By the time we get to the third Meditation, he freely discusses both mind and body. So after his

meditations are done, it is actually better to call Descartes a "dualist" instead of an idealist, because he has the duality of

the two substances, mind/ideas and body/physical matter.