PHL240H1 Lecture Notes - Lecture 4: Extensional Context, Cogito Ergo Sum
Document Summary
Leibniz"s law: if x is numerically identical to y, then x and y have exactly the same properties. Leibniz: numeric identity is sufficient for qualitative identity. Qualitative identity: two things are exactly the same thing in every way. Two duplicates have the same qualitative identity: descartes: mind body separation: i cannot doubt the existence of my mind, i can, however, doubt the existence of my body. Problem: intensional context: a sentence s Whether or not we can doubt the existence of something is not a property of that thing. When you add terms like believe" and doubt" in there, you get a problem. May have something to do with intentional contexts like these, talk not only about what objects do, and also about what subjects do. When talking about lous believes superman/clark flies, we aren"t talking only about clark but also about. Same sort of thing applies to doubt". Doubt also opens up an intensional context.
