Psychologia Empirica

the determinations and directions of [human actions] are explained in no less an intelligible manner, and are deduced a priori from the nature of the soul, than the actions of bodies and the changes depending thereon in the universe are wont to be explained in physics today. We shall provide ocular proof when, once metaphysics is completed and natural law has been brought to its conclusion, we treat of ethics according to our method. Then, even to one running through it with a fleeting eye, it will be evident how great the use of empirical psychology is in the practice of morals. Indeed, the same will already become clear in universal practical philosophy, in which we shall deliver the general theory of that practice. Empirical psychology also has a notable use, hitherto unnoticed, in investigating and developing the very notion of natural law and natural obligation, which will again become clear from universal practical philosophy. Moreover, in natural law, that most noble part of duties toward oneself—which is to say, those duties which comprise duties toward the soul—cannot be duly established without a thorough understanding of the faculties of the soul: a fact that will be abundantly evident from the Corpus of natural law, such as we shall provide in its most enriched form. But especially in that part of moral philosophy, semiotics, which is the Art of con-jectan-