Complex sentence: Thus, a person's mind cannot be the true cause of his hand moving, nor can a physical wound be the true cause of mental anguish-in other words, the mental cannot cause the physical and vice versa.
Split into simpler sentences: Thus, a person's mind cannot be the true cause of his hand's moving, nor can a physical wound be the true cause of mental anguish. In other words, the mental cannot cause the physical and vice versa.