  The reason Leibniz mentions the different laws governing the different possible worlds is that the systems of laws and their effects serve as criteria by which God chooses a world. We know that, for Leibniz, God chooses the “best of all possible worlds.” In §6 the Discourse on Metaphysics, however, we learn that this means that God chooses the world that is simplest in hypotheses (or laws) and richest in phenomena. Thus, while one might be tempted to see natural laws as derivative of the actual properties and perceptions of individual substances, in fact they are objects of God's choice.