How does epiphenomenalism describe the role of mental events in causing physical actions?

In the philosophy of mind, epiphenomenalism posits that mental events—such as thoughts, beliefs, or desires—are by-products of physical brain states but possess no causal power themselves.12

According to this view, mental events are entirely caused by prior physical events in the brain or body, yet they exert no influence back upon the physical world. When a person wills a bodily movement, the movement is caused exclusively by preceding physical states of the body, not by the mental act of willing. The mental event is merely an effect, or "epiphenomenon," that accompanies the physical process.132

Because epiphenomenalism maintains that the physical world is a closed system governed by causality and conservation laws, it avoids the conflict between mental phenomena and the laws of physics that arises in dualistic interactionism. However, this position faces significant criticism: if mental events have no causal role in the world, it becomes difficult to justify their existence, leading some to argue that such a view invites eliminativism—the denial that mental phenomena exist at all.32