Abstract
Scientific methodologies in 17-18th centuries are very important when we think of the relation of philosophy and science in this period. Particularly interesting among them is that of Leibniz's philosophy. His method of finding laws of natural sciences was a so-called hypotheticodeductive method. What is quite remarkable in his methodology is that he not only shows empirically valid criteria for finding laws, in spite of his extreme rationalistic tendencies on one hand, but also delves into the grounds for the hypothetico-deductive method in terms of God's perfection. In this latter point, we can recognize one of the proper roles of philosophy, very clearly distinguished from but united very organistically with those of science.