A popular argument against dualism (in the folk world, not among professional philosophers) is that the mind can be affected by taking drugs, or by brain damage, and so on. So clearly, the mind must be created by or be caused by the brain, and hence dualism is false. Here is the argument formally:
1. All mental events can be affected by physical events
2. No immaterial things can be affected by physical events
3. Therefore, no mental event is immaterial (i.e., dualism is false)
But no dualist would accept premise 2. Of course dualists think that the (immaterial) mind can be affected by matter! Stub your toe, experience the (immaterial) mental event of pain.
This ever-popular argument, perhaps the main argument against dualism in the world of the layman, is unsound.