 It should not be inferred that this appetitive tendency to change is entirely governed by efficient causation only. For in Leibniz’s view, value and final causes are not excluded from the action of the mind, the change of mental states. As he says in section 13 of the Discourse on Metaphysics (1686), just as “God will always do the best, … a man shall always do … that which appears to him to be the best” (G IV, 438/A&amp;G 46). Appearance, of course, has to do with perception; doing, with appetition. So this principle of human action applies directly, as one would expect, to the two key factors of monadic interior life, only with the role of value, or an end in view, now more clearly in focus. This is why Leibniz says that, at the level of bodies (that is, for Leibniz, at the level of well-founded phenomena), all occurs according to the laws of efficient causes; whereas with respect to perceptions and appetites (or at least with some of these—interpretations differ here) all occurs according to the laws of final causes. And although both types of causation can be found at both levels (cf. Carlin 2006), there is no clash here given the harmony of final and efficient causes in Leibniz’s system.