I found the following argument in Fesar's book, Philosophy of Mind. I would like to know how you would respond to it.

Here is the argument: "A Cartesian immaterial substance, being outside space, is outside this universe. For it to affect the physical world, and in particular the brain, it would have to introduce energy into the physical universe; and for the brain in turn to affect an immaterial substance, it would seemingly transfer energy out of the physical universe. Either way, the amount of energy in the physical universe would fail to be constant. So the very idea of causal interaction between Cartesian material and immaterial substances seem to violate the law of physics."

__________________
Curt Hayashida
member, Community Bible Church (Non-denominational)
Vallejo, CA