1. Modern science has shown that what goes on in our bodies can be explained in physical terms, as the result of various electrochemical or biomechanical interactions.
But what about what goes on in our minds? Can our thoughts be explained physically?
2. Theories of Reality:
Idealism: the doctrine that all that exists are minds and their contents.
Materialism: the doctrine that all that exists are material objects.
Dualism: the doctrine that reality contains both mental and material things.
3. Cartesian dualism maintains that mental states are states of an immaterial substance that interacts with the body.
4. Descartes arrived at this view by considering how we come to know things.
We know something only if it’s certain.
Most of what we think we know is based on sense experence.
But we can’t be certain of anything we’ve learned through sense experience.
5. The Dream Thought Experiment:
“How often has it happened to me that in the night I dreamt that I found myself in this particular place…while in reality I was lying undressed in bed.”
6. The Evil Demon Thought Experiment:
“How do I know that [an evil demon] has not brought it to pass that there is no earth, no heaven, no extended body, no magnitude, no place, and that nevertheless they seem to me to exist just exactly as I now see them?”
7. Descartes cannot doubt that he is thinking, for doubting is a type of thinking.
And Descartes can’t doubt anything unless he exists.
So Descartes claims that he can be absolutely certain of one thing, namely, “I think, therefore I am.”
8. The Conceivability Argument
It’s conceivable for me to exist without having a body.
Whatever is conceivable is possible.
Therefore, it’s possible for me to exist and not have a body.
If it’s possible for me to exist without having a body, then having a body is not essential to me.
Therefore, having a body is not essential to me.
9. The Conceivability Argument
It’s inconceivable for me to exist without having a mind.
Whatever is inconceivable is impossible.
Therefore, it’s impossible for me to exist and not have a mind.
If it’s impossible for me to exist without having a mind, then having a mind is essential to me.
Therefore, having a mind is essential to me.
10. Descartes has proven that he is a thing that thinksBut physical things, he claims, cannot think.
So, he concludes, he (his mind) is a non-physical thing.
11. The Divisibility Argument
If minds are identical to bodies, then whatever is true of minds is true of bodies, and vice versa.
But minds are indivisible and bodies are divisible.
Therefore, minds are not identical to bodies.
12. The Problem of Interaction:
Descartes believes that our minds affect our bodies, and vice versa.
But how can a…