Now if we go from knowledge to its content, in which the Idea becomes sundered, and thereby organizes itself more completely into a scientific system, this content, according to Plato, begins to fall into three parts which we distinguish as the logical, natural, and mental philosophy. The logical Philosophy the ancients called dialectic, and its addition to philosophy is by the ancient writers on the subject ascribed to Plato (Vol. I. p. 387). This is not a dialectic such as we met with in the Sophists, which merely brings one’s ideas altogether into confusion, for this first branch of Platonic philosophy is the dialectic which moves in pure Notions—the movement of the speculatively logical, with which several dialogues, and particularly that of Parmenides, occupy themselves. The second, according to Plato, is a kind of natural philosophy, the principles of which are more especially propounded in the Timæus. The third is the philosophy of the mind—an ethical philosophy—and its representation is essentially that of a perfect state in the Republic. The Critias should be taken in connection with the Timæus and the Republic, but we need not make further reference to it, for it is only a fragment. Plato makes these three dialogues one connected conversation. In the Critias and the Timæus the subject is so divided that while the Timæus dealt with the speculative origin of man and of nature, the Critias was intended to represent the ideal history of human culture, and to be a philosophical history of the human race, forming the ancient history of the Athenians as preserved by the Egyptians. Of this, however, only the beginning has come down to us.[29] Hence if the Parmenides be taken along with the Republic and the Timæus, the three together constitute the whole Platonic system of philosophy divided into its three parts or sections. We now wish to consider the philosophy of Plato more in detail in accordance with these three different points of view. 1. DIALECTIC.