The philosophy of Hegel appeals to an historical criterion: the ideas of men have a succession in time as well as an order of thought. But the assumption that there is a correspondence between the succession of ideas in history and the natural order of philosophy is hardly true even of the beginnings of thought. And in later systems forms of thought are too numerous and complex to admit of our tracing in them a regular succession. They seem also to be in part reflections of the past, and it is difficult to separate in them what is original and what is borrowed. Doubtless they have a relation to one another--the transition from Descartes to Spinoza or from Locke to Berkeley is not a matter of chance, but it can hardly be described as an alternation of opposites or figured to the mind by the vibrations of a pendulum. Even in Aristotle and Plato, rightly understood, we cannot trace this law of action and reaction. They are both idealists, although to the one the idea is actual and immanent,--to the other only potential and transcendent, as Hegel himself has pointed out (Wallace's Hegel). The true meaning of Aristotle has been disguised from us by his own appeal to fact and the opinions of mankind in his more popular works, and by the use made of his writings in the Middle Ages. No book, except the Scriptures, has been so much read, and so little understood. The Pre-Socratic philosophies are simpler, and we may observe a progress in them; but is there any regular succession? The ideas of Being, change, number, seem to have sprung up contemporaneously in different parts of Greece and we have no difficulty in constructing them out of one another--we can see that the union of Being and Not-being gave birth to the idea of change or Becoming and that one might be another aspect of Being. Again, the Eleatics may be regarded as developing in one direction into the Megarian school, in the other into the Atomists, but there is no necessary connexion between them. Nor is there any indication that the deficiency which was felt in one school was supplemented or compensated by another. They were all efforts to supply the want which the Greeks began to feel at the beginning of the sixth century before Christ,--the want of abstract ideas. Nor must we forget the uncertainty of chronology;--if, as Aristotle says, there were Atomists before Leucippus, Eleatics before Xenophanes, and perhaps 'patrons of the flux' before Heracleitus, Hegel's order of thought in the history of philosophy would be as much disarranged as his order of religious thought by recent discoveries in the history of religion.