1.) Descartes restates the horror and difficulty of his universal doubt. This is not a mere recapitulation: universal doubt is extensively used in Chapter II.
2.) Any object admits of Cartesian doubt.
3.) Any extrinsic cause of thoughts can be doubted because the self might be the cause. This is the first introduction of the idea of a self. Through a well-known line of reasoning, Descartes concludes I am, I exist. Thought in no way is seen as a principle or condition of existence, it simply provides a context within which ones self existence shows itself as indubitable and necessary. We need not start with thought and then conclude to existence, we can start with the indubitablity of existence, and then manifest or articulate this indubitability by considering thought. The fundamental Cartesian claim is simpler than “the cogito” – his fundamental claim is I am. (It is hard not to suspect that Descartes was aware the biblical overtones of the claim.)
4- 5.) Having established that he is, Descartes seeks to establish what he is. He first raises the question whether he is a rational animal, but rejects this line of inquiry since he says it will take too much time and is too complicated. I was puzzled and irritated by this argument for years: mere time considerations should not dictate whether something is worth following or not. My irritation is not all that reasonable, however, since all sorts of potential answers to questions are judged to be false because they are too complicated. This is particularly true so far as one is working under a Cartesian doubt: complicated, and especially open-ended answers are intrinsically dubious and so must be rejected. But Descartes second argument for why he rejects the idea of a rational animal is much better: he is only going to consider answers that arise spontaneously and naturally, in light of his own reason. In this light he first considers that he knows what a body is.
6-9.) Descartes concludes he is a thinking thing, as opposed to being a subject that depends on body in any way.
What is physical or depends on the physical has an existence that can be doubted by Cartesian doubt.
My own existence cannot be doubted by Cartesian doubt.
My own existence is not physical nor does it depend on the physical.
A supplemental argument:
If my existence as such intrinsically depended on something unknown to me, my existence as such could be unknown to me
But my existence is not unknown to me.
10.) It is strange to say that he is a self which is in no way imaginable is when things that are imaginable and sensible are so much more well known. Descartes is looking for a supplemental argument to manifest this more clearly.
11-end.) The Piece of Wax. The piece of wax is a series of arguments, all of which are remarkable and become more and more so with each reading. the argument is a reductio:
This piece of wax is a (paradigmatic) single physical thing.
A single physical thing must persevere throughout time as what it is.
The senses do not provide any information that must persevere throughout time as what it is.
The senses do not provide any information about the piece of wax.
The argument can be simpler
What knows by senses does not know natures (that is, single realities that persist throughout time)
I know natures.
Knowledge of this is thus by a direct vision or intuition of the intellect.
Descartes raises an objection: even if the individual sensible qualities can change, something sensible remains, e.g. an extension, the motion of things, or the changes of one thing to another. Descartes responds with a dilemma-argument:
By “change” or “extension” one either means change or extension in general, or a this concrete extended shape or change.
If one means change or extension in general, this is not known by sense.
If one means this concrete shape or change, then there are infinite possibilities for any object or medium, and a sense organ cannot know infinite possibilities.
13.) Arguments continue:
Identical sensations can be judged to be different things (like when we see a wax statue and say it is wax)
therefore, it is not necessary that any judgment be by sensation. `
My knowledge is different from the knowledge of a non-human animal
My sensation is the same as a non-human animal
Therefore, my knowledge is not by sensation.
15.) An interesting argument a fortiori:
If I judge that wax, or some other object exists, it is because I touch it or see it.
But then, a fortiori, I am even more certain that I myself exist, since I have an even better sort of knowledge in the same order.