Monism

Varieties of dualism in which mind can causally affect matter have come under strenuous attack from different quarters, especially starting in the 20th century. How can something totally immaterial affect something totally material? That's the basic problem of causal interaction. This problem can be broken down into three parts.

First, it is not clear where the interaction would take place. For example, burning one's fingers causes pain. Apparently there is some chain of events, leading from the burning of skin, to the stimulation of nerve endings, to something happening in the peripheral nerves of one's body that lead to one's brain, to something happening in a particular part of one's brain, and finally resulting in the sensation of pain. But pain is not supposed to be spatially localizable. It might be responded that the pain "takes place in the brain." But, intuitively, pains are not located anywhere. A dualist might stick to his guns and insist that pains are not located anywhere; but the brain event that immediately leads to the pain is located in the brain." But the result is a very strange causal relation: The cause is located in a particular place but the effect is not located anywhere.

This may not be a devastating criticism. However, there is a second problem about the interaction. Namely, the question of how the interaction takes place. It may be supposed that this is solely a a matter for science to resolve -- scientists will eventually discover the connection between mental and physical events. But philosophers also have something to say about the matter, since the very notion of a mechanism which explains the connection between the mental and the physical would be very strange, at best. For example, compare such a mechanism to a mechanism that is well understood. Take a very simple causal relation, such as when a cue ball strikes an eight ball and causes it to go into the pocket. What happens in this case is that the cue ball has a certain amount of momentum as its mass moves across the pool table with a certain velocity, and then that momentum is transferred to the eight ball, which then heads toward the pocket. Compare this to the situation in the brain, where one wants to say that a decision causes some neurons to fire and thus causes a body to move across the room. The intention to "cross the room now" is a mental event and, as such, it does not have physical properties