On the division of philosophical disciplines and the unity of philosophical knowledge according to Aristotle

In this article, the author addresses the problems of theoretical knowledge according to Aristotle, who divided all sciences into three parts: theoretical, practical, and productive. The first among the sciences are theoretical sciences or theoretical philosophies (φιλοσοφίαι θεωρητικαί) - physics, mathematics, and theology. Each of them deals with some kind of essence or a part of being. Why Aristotle divides the philosophical disciplines that way and what guarantees the unity of philosophical knowledge? By considering first principles of apodictic knowledge, the author concludes that this is possible if one introduces another form of knowledge, which properly concerns with the first principles of being and thought.