Interactionism, whatever its philosophical difficulties, is close to what ordinary religious and moral life assumes by default: prayer is generally understood to be a mental or spiritual act capable of producing real effects, whether in the world or in the one praying, and most traditions describing an immortal soul also describe that soul as capable of directing the body it inhabits, not merely watching it move. Occasionalists reject this directness for theological reasons, insisting that only God is a true cause and that apparent mind-body interaction is really God's continuous, coordinated action; epiphenomenalists reject it for a different, scientific reason, holding that causation runs only from body to mind and never back, so that mental states are real but causally inert bywords for what the brain was always going to do anyway.
Interactionism's philosophical defenders argue that denying real mental causation makes nonsense of deliberation, moral responsibility, and the very act of arguing for any position at all, since arguing is itself supposed to be a case of reasons, mental items, producing conclusions and then actions; its critics answer that this practical usefulness does not settle the deeper question of how the interaction is supposed to work.