Why does preestablished harmony avoid direct interaction between mind and body?

In the philosophy of mind, the doctrine of preestablished harmony, proposed by Gottfried Wilhelm Leibniz, avoids direct interaction between mind and body by positing that no true causality exists between them.1

Rather than interacting, mental and physical phenomena are viewed as two series of perfectly correlated events. Leibniz argued that these substances are so radically different in nature that it is inconceivable for them to influence one another. Instead, God synchronized the entire universe at the beginning of time in a single creative act.21

Under this framework, when a change occurs in one monad—the fundamental psychophysical entities of his system—every other monad reflects that change spontaneously. The relationship is often compared to two perfectly synchronized clocks that keep the same time without needing any mechanical connection to influence each other. Consequently, the appearance of interaction is merely an illusion created by this original, divine coordination.12