It is an often-quoted observation of Friedrich Schlegel’s that every man is born either a Platonist or an Aristotelian. If we narrow the remark to the only class which, perhaps, its author recognised as human beings, namely, all thinking men, it will be found to contain a certain amount of truth, though probably not what Schlegel intended; at any rate something requiring to be supplemented by other truths before its full meaning can be understood. The common opinion seems to be that Plato was a transcendentalist, while Aristotle was an experientialist; and that this constitutes the most typical distinction between them. It would, however, be a mistake to suppose that the _à priori_ and _à posteriori_ methods were marked off with such definiteness in Plato’s time as to render possible a choice between them. The opposition was not between general propositions and particular facts, but between the most comprehensive and the most limited notions. It was as if the question were now to be raised whether we should begin to teach physiology by at once dividing the organic from the inorganic world, or by directing the learner’s attention to some one vital act. Now, we are expressly told that Plato hesitated between these two methods; and in his Dialogues, at least, we find the easier and more popular one employed by preference. It is true that he often appeals to wide principles which do not rest on an adequate basis of experimental evidence; but Aristotle does so also, more frequently even, and, as the event proved, with more fatal injury to the advance of knowledge. In his _Rhetoric_ he even goes beyond Plato, constructing the entire art from the general principles of dialectics, psychology, and ethics, without any reference, except for the sake of illustration, to existing models of eloquence.