just seems like they do. Whenever we perceive a monad to be the cause of something, other monads are created in such a way as to seem like they are affecting the others. According to Leibniz, the entire universe was created by God to be in a pre-established harmony, so nothing in the universe actually influences anything else. Considering psychophysical parallelism thusly, you could imagine the mind and body as two identical clocks. The clocks will always be in agreement because of the pre-existing harmony between them, but will never interact. And like the two clocks, no interaction or causation among the monads that compose the mind and body is necessary because they are already synchronized. See also Metaphysical naturalism Mind–body dichotomy Philosophy of Baruch Spinoza: Parallelism Spinozism: Parallelism Notes References Theory of mind