In the Second Meditation, Descartes seeks to show that the mind is better known than the body. (It says so right in the title.)
I’m going to present a short outline of the major parts of this meditation with some notes on what to look for. The number-letter combinations in parentheses refer to pages and columns in the textbook: (43L) means “the left column of page forty-three.”
There are four main parts.
I cannot be mistaken about this, even I am dreaming or being deceived by a supernatural power like an evil demon. (43R) This is one of the more famous arguments in philosophy so you will want to understand how it goes.
Look at what he thinks a body is (44L). We are going to use this later in the course.
His argument that he cannot know that he is a body goes pretty quickly: see the top of 44R.
Look at page 44, right column near the top
What about thinking? Here I make my discovery: Thought exists; it alone cannot be separated from me. I am; I exist — this is certain. But for how long? For as long as I am thinking; or perhaps it could also come to pass that if I were to cease all thinking I would then utterly cease to exist. At this time I admit nothing that is not necessarily true. I am therefore precisely nothing but a thinking thing; that is, a mind, or intellect, or understanding, or reason — words whose meaning I was previously ignorant. Yet I am a true thing and am truly existing; but what kind of thing? I have said it already: a thinking thing. (Descartes [1641] 2019, 44R)
Descartes starts with “thought exists” and then a few sentences later says that “a thinking thing” exists. Is he allowed to treat those as basically the same thing? We will want to talk about that.
We will also talk about what the thinking thing is.
After scratching our heads about what a thinking thing is, you might think that our understanding of bodies is superior. After all, you can see and feel a body. (And taste, hear, and smell it too, quite often.) Descartes is going to deny this.
He does so using an example of a piece of wax (45R). We are going to talk about how that example works.
The upshot of the example is supposed to be that the senses do not tell you what the body of the piece of wax is really like. Rather, you have to use what he calls the “intellect” to understand that, in this case and, presumably, all others.
I now know that bodies are not, properly speaking, perceived by the senses or by the faculty of imagination, but by the intellect alone, and that they are not perceived through their being touched or seen, but only through their being understood. (Descartes [1641] 2019, 47L)
Conclusion: his knowledge of bodies is the same in kind as his knowledge of his own mind. Both are known by reason. And he knows his own mind “more easily and more evidently” than he knows about external bodies (Descartes [1641] 2019, 47L).