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Possible examples of a

priori knowledgebachelors are unmarried

2+2=4

There cannot be a round square

Any logical truththe connectionbetween premises and conclusion in avalid argument

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The dream argument calls intoquestion knowledge based on

experience, but it leaves a prioriknowledge untouched

But the evil demon argument

questions also a priori knowledge

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The EVIL DEMON!

It is possible that there is a demon,with nearly godlike powers, who aims

to deceive me. Therefore it is possible that all my

beliefs, are the result of the deceptive

powers of a demon Therefore I cannot trust any of my

beliefs

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Meditation 2

Descartes now tries to discover somebelief or beliefs that can be known

with certainty. These beliefs wouldhave to be true even if there is ademon

He finds one: I exist. But could an evil demon deceive him

(or you) about your own existence?

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Descartes answers no. Deceptionrequires that there be something to be

deceived.Even if all my thoughts are mistaken,

the thoughts must exist in order for

them to be mistakenEverytime I reflect on my thinking I can

know with absolute certainty that I

exist.

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But what sort of thing isthis I

Am I a rational animal?

Am I a human being?

What is essential to this I that Iknow to exist?

Essentially, what I am is not humanbeing, not rational animal, but athinking thing

Why?

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The knowledge that I am human or ananimal, or even have any body, is still

in doubt. A demon can deceive meabout these things. So I cannot knowanything about my physical being. But

there is something I know. What Iknow is the residuum, it is what is leftover after all that can be doubted isdoubtedthinking, consciousness.

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Solipsism!

Solipsism is a view that can only bestated in the first person.

My mind is all that exists, everythingelse only exists as I experience it.

There are few if any solipsists. But is

there any way to refute solipsism?

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The piece of wax

Therefore we know the mind withmuch more clarity than we know the

body. But this is hard to believe. Its easy to

think that knowledge of the physical

world is much more concrete,tangible, and that the mind issomehow mysterious

The piece of wax example shows us

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Take a piece of wax, melt it.

All the sensible properties change

Yet we still believe, we still take thewax to be the same thing

This shows: [supposed] knowledge of

physical things is based on the mind.We need to think to know the physicalworld

Our concept of the physical world isnot a bundle of sensible qualities.

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What we understand when weunderstand that the piece of wax is

the same is a flexible, extendedsubstance

It is what underlies or causes our

perceptions, not what we directlyperceive

Descartes is foreshadowing future

conclusions in the Meditations.