Problems of Dualism
How can there be mind-body interaction? When I take a bite of an apple, it produces taste experiences in my mind by way of my body. How does that work if mind and body are different substances?
I might choose to act out of free will. How can the mind be free in a universe otherwise determined by natural law?
How can we verify the existence of the external world? Descartes relies on God in his proof of the external world. But today God is not providing this kind of support in philosophy.
How do we know that other people are conscious? Indeed how do we know that they exist? Perhaps you live in a world of robots or zombies. How would you know? All you know are the experiences in your mind. Few claim to be solipsists—people who think that only they themselves exist. It would make no sense for them to discuss their position. Who would they tell?
Descartes equated animals with nonconscious, mindless machines because he saw insufficient evidence in them of thought processes. Most of us would disagree. Perhaps all animals are conscious. Maybe only some are. If so, where do we draw the line between animals that are conscious and those that are not?
For Descartes, the essence of the mind is thought. That is what makes it the thing it is. But what happens if we go to the doctor and he gives us general anesthesia? Do we cease to exist? What happens when we wake? Is it a different mind that comes into being? The same thing can be said about sleep. Do we exist if we fall into a state of dreamless sleep? Descartes claimed we are always conscious in sleep, but there is insufficient support for this claim.
For Descartes, the self is a thinking thing, but how can that be? How can the self be defined in terms of fluctuating thought patterns and experiences? What allows for identity over time?
The philosophy of mind since Descartes has been much occupied with these problems. Descartes has also had an influence outside philosophy and, by examining the history of how the mind-body problem has been approached, we can come to better understand the current field of consciousness studies and the questions being raised.