There is a quite generally held opinion that the Aristotelian and Platonic philosophies are directly opposed, the one being idealistic and the other realistic, and that, indeed, in the most trivial sense. For Plato is said to have made the ideal his principle, so that the inward idea creates from itself; according to Aristotle, on the contrary, we are told that the soul is made a tabula rasa, receiving all its determinations quite passively from the outer world; and his philosophy is thus mere empiricism – Locke’s philosophy at its worst. But we shall see how little this really is the case. In fact Aristotle excels Plato in speculative depth, for he was acquainted with the deepest kind of speculation – idealism – and in this upholds the most extreme empirical development.