The historian of philosophy is also a philosopher, and it is not appropriate for him to put himself in the position of a parrot, and limit his task to narrating the sayings of philosophers without carefully considering and judging them. In this book, the author addresses the issues for their own sake, trying to reveal the face of truth in them. The title indicates that he presents the study of the mind, just as the worker presents the examination of the machine before starting to use it. All people believe in their reason and senses to begin with, and the philosopher who believes in the truth of the mind and senses can go along with them and break into logic and praise natural philosophy, deferring the criticism of knowledge to its logical place, which is the science of metaphysics, the most general of the sciences, which is therefore specialized in examining the most general issues.