In several of the later dialogues Plato is occupied with the connexion of the sciences, which in the Philebus he divides into two classes of pure and applied, adding to them there as elsewhere (Phaedr., Crat., Republic, States.) a superintending science of dialectic. This is the origin of Aristotle's Architectonic, which seems, however, to have passed into an imaginary science of essence, and no longer to retain any relation to other branches of knowledge. Of such a science, whether described as 'philosophia prima,' the science of ousia, logic or metaphysics, philosophers have often dreamed. But even now the time has not arrived when the anticipation of Plato can be realized. Though many a thinker has framed a 'hierarchy of the sciences,' no one has as yet found the higher science which arrays them in harmonious order, giving to the organic and inorganic, to the physical and moral, their respective limits, and showing how they all work together in the world and in man. Plato arranges in order the stages of knowledge and of existence. They are the steps or grades by which he rises from sense and the shadows of sense to the idea of beauty and good. Mind is in motion as well as at rest (Soph.); and may be described as a dialectical progress which passes from one limit or determination of thought to another and back again to the first. This is the account of dialectic given by Plato in the Sixth Book of the Republic, which regarded under another aspect is the mysticism of the Symposium. He does not deny the existence of objects of sense, but according to him they only receive their true meaning when they are incorporated in a principle which is above them (Republic). In modern language they might be said to come first in the order of experience, last in the order of nature and reason. They are assumed, as he is fond of repeating, upon the condition that they shall give an account of themselves and that the truth of their existence shall be hereafter proved. For philosophy must begin somewhere and may begin anywhere,--with outward objects, with statements of opinion, with abstract principles. But objects of sense must lead us onward to the ideas or universals which are contained in them; the statements of opinion must be verified; the abstract principles must be filled up and connected with one another. In Plato we find, as we might expect, the germs of many thoughts which have been further developed by the genius of Spinoza and Hegel. But there is a difficulty in separating the germ from the flower, or in drawing the line which divides ancient from modern philosophy. Many coincidences which occur in them are unconscious, seeming to show a natural tendency in the human mind towards certain ideas and forms of thought. And there are many speculations of Plato which would have passed away unheeded, and their meaning, like that of some hieroglyphic, would have remained undeciphered, unless two thousand years and more afterwards an