The question which Plato has raised respecting the origin and nature of ideas belongs to the infancy of philosophy; in modern times it would no longer be asked. Their origin is only their history, so far as we know it; there can be no other. We may trace them in language, in philosophy, in mythology, in poetry, but we cannot argue _à priori_ about them. We may attempt to shake them off, but they are always returning, and in every sphere of science and human action are tending to go beyond facts. They are thought to be innate, because they have been familiar to us all our lives, and we can no longer dismiss them from our mind. Many of them express relations of terms to which nothing exactly or nothing at all _in rerum naturâ_ corresponds. We are not such free agents in the use of them as we sometimes imagine. Fixed ideas have taken the most complete possession of some thinkers who have been most determined to renounce them, and have been vehemently affirmed when they could be least explained and were incapable of proof. The world has often been led away by a word to which no distinct meaning could be attached. Abstractions such as ‘authority,’ ‘equality,’ ‘utility,’ ‘liberty,’ ‘pleasure,’ ‘experience,’ ‘consciousness,’ chance,’ ‘substance,’ ‘matter,’ ‘atom,’ and a heap of other metaphysical and theological terms, are the source of quite as much error and illusion and have as little relation to actual facts as the ‘ideas’ of Plato. Few students of theology or philosophy have sufficiently reflected how quickly the bloom of a philosophy passes away; or how hard it is for one age to understand the writings of another; or how nice a judgment is required of those who are seeking to express the philosophy of one age in the terms of another. The ‘eternal truths’ of which metaphysicians speak have hardly ever lasted more than a generation. In our own day schools or systems of philosophy which have once been famous have died before the founders of them. We are still, as in Plato’s age, groping about for a new method more comprehensive than any of those which now prevail; and also more permanent. And we seem to see at a distance the promise of such a method, which can hardly be any other than the method of idealized experience, having roots which strike far down into the history of philosophy. It is a method which does not divorce the present from the past, or the part from the whole, or the abstract from the concrete, or theory from fact, or the divine from the human, or one science from another, but labours to connect them. Along such a road we have proceeded a few steps, sufficient, perhaps, to make us reflect on the want of method which prevails in our own day. In another age, all the branches of knowledge, whether relating to God or man or nature, will become the knowledge of ‘the revelation of a single science’ (Symp. 210, 211), and all things, like the stars in heaven, will shed their light upon one another. MENO. _PERSONS OF THE DIALOGUE._