It can have its effect only through the intervention of God, inasmuch as in the ideas of God a monad rightly demands that God, in regulating the rest from the beginning of things, should have regard to itself.

Men act like brutes in so far as the sequences of their perceptions arise through the principle of memory only, like those empirical physicians who have mere practice without theory.

It follows from what we have just said, that the natural changes of monads come from an internal principle, since an external cause would be unable to influence their inner being.

Gottfried Leibniz Quotes