PHI 205 Lecture Notes - Lecture 13: Dream Argument, Mental Body

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Published on 21 Mar 2017
Rationalist Thought
Knowledge a priori vs. knowledge a posteriori
Descartes is looking for knowledge that can be a priori
Descartes’ First Meditation
The principle of reasonable doubt:
o “Reason now leads me to think that I should withhold my assent from opinions
which are not completely certain and indubitable just as carefully as I do from
those which are patently false. So, for the purpose of rejecting all of my opinions,
it will be enough if I find in each of them at least some reason for doubt”
Is there some reason to doubt that these “hands or this whole body are mine”?
o How do I tell if I’m just dreaming that these are my hands or if they actually are?
The dream argument
o Main argument that Descartes uses
o Since we can’t be sure if we are awake or asleep, it is reasonable to doubt whether
are not these are actually your hands, etc.
o Any belief that would be based on considerations of the senses aren’t going to be
compatible with true knowledge
The evil demon
o Some “deceiver of supreme power and cunning who is deliberately and constantly
deceiving me” and tricking him into thinking certain things exist in a certain way,
etc., when they actually exist in another way.
Descartes’ Second Meditation
“…I will proceed in this way until I recognize something certain, or, if nothing else, until
I at least recognize for certain that there is no certainty.”
What could we know, if we follow the principle of reasonable doubt and the dream
argument makes it doubtful that “these are my hands,” etc.?
o What is left, if anything, that we could know?
o Against this backdrop, Descartes tries to convince the reader that there is
something that we can know indubitably.
The case of self-knowledge: I think therefore I am
o “I have just said that I have no senses and no body…Am I not so bound up with a
body and with senses that I cannot exist without them? But I have convinced
myself that there is absolutely nothing in the world, no sky, no earth, no minds, no
bodies. Does it now follow that I too do not exist? No: if I convinced myself of
something, then I certainly existed.”
o Says that the evil demon also proves his existence, because he must obviously
exist to be acted upon in that way.
o “I must finally conclude that this proposition, I am, I exist, is necessarily true
whenever it is put forward by me or conceived in my mind.”
o It’s indubitable that you exist if you have these thoughts
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