of empirical data, scientific knowledge, to aid them in their speculations, but they had not successfully applied them to the science of mind. The postulate of Descartes ("I think, therefore I am"), the God of Spinoza, and the idealism of Kant, were no nearer the ultimate generalization than the speculations of the earliest thinkers. They one and all strove to reduce all imaginable diversities to one principle. The vastly superior scientific knowledge of the modern thinkers only seemed to increase the field of their diversities, it did not bring them to the ultimate simplicity. This ultimate simplicity has many names; in seeking for it, it has been denominated the ultimate unity, truth, fact, principle, cause, substance, energy, force, existence, or reality. Thales, in the paucity of his scientific experience, thought that it was water; Anaximenes, that it was air; Diogenes of Apollonia, that it was living air; Anaximander of Miletus, that it was the eternal motion of the infinite; Descartes considered it a dual principle of mind and matter; Spinoza calls it God. Kant attributes this ultimate reality to mind alone, and Herbert Spencer calls it the "persistence of force." Where is the progress of the intervening twentyfive centuries? Surely it is in scientific knowledge, and not in pure philosophy. Will it be too much to ask the reader to believe that this ultimate reality or principle is plainly and unmistakably confronting us wherever we turn, that it alone accounts for every experience, and that the only reason why it has so long escaped us is, that it is an inseparable and primordial quality of our very existence? It is too near to be seen, too easy to understand; and for this reason, and only for this reason, it is difficult to explain. If singleness of mind is strength, then indeed it requires the greatest intellectual power to grasp this fact. It would seem, though, that the requisite condition of the mind to appreciate this truth is not that of great tension, or a very high degree of training, but a self-discipline, a submission to the power of facts, a renunciation of mental or verbal conceit; in a word, the very thing in an intellectual sense that religion demands of us in a sentimental sense in order to know God. To present the argument in a scientific form, the whole burden is to prove that matter and space are words which have the same ultimate signification. Matter is clearly a generalization of the statical side of phenomena. Under analysis matter disappears in motion. Space is simply our term for infinity or extension, and therefore the argument turns upon the point whether the universe is a plenum or not. In further support of the fact that it is, I refer the reader to an argument in "Problems of Life and Mind," by G. H. Lewes, as a powerful corroboration of this view, that matter and space are terms which are logically indistinguishable. This argument, entitled "Action at a Distance," is given entire in Chapter XV., Part II., of the present work. Some time after I had made an attempt' to explain the above theory of the identity of matter and space, this essay gave me unexpected assistance. Although it does not state in terms that matter and space are the same thing, this is an irresistible inference from the argument. The question is one of such transcendent importance in philosophy, and this argument by Lewes seems to me so conclusive, that I thus refer to it in advance. The consequences of this reasoning are momentous. Unless this theory stand, the categories of thought, or ultimate realities, will remain discrete, as we find them in Herbert Spencer's "Psychology," and in all other modern philosophies, namely, Space, Time, Matter, Force, and Motion. Some writers add Cause, but it is now generally admitted that Cause stands for merely one aspect of every phenomenon, the obverse side of which is Effect, cause being thus a term denoting a purely logical distinction. Others, again, postulate Consciousness as an ultimate reality. Spencer, for instance, distinctly declares consciousness to be an irreducible principle, but this error is fully met and set aside by Lewes. 'An anonymous brochure published in 1881. The interdependence of the five ultimate terms, abovenamed, has not as yet been successfully demonstrated; but if matter and space are admitted to be the same reality, under different aspects, the difficulty at once disappears; for then motion becomes the ultimate reality and space and time become its obverse aspects. Space and time have no separate existence apart from motion; their identity is merged in this ultimate fact. As stated above, the amount of mental reorganization or reform necessary to grasp this simplest of all facts is such as to place it practically beyond the reach of minds that have been trained to cherish the distinctions which this theory would destroy. We have met many people of scientific and philosophic training who are logically incapacitated for receiving this truth; they would no more believe that matter and space were the same thing than a devotee would surrender his faith. It is, therefore, to the younger class of thinkers that we must appeal,-thinkers who have not committed themselves too deeply, who are open to conviction, who are hospitable to new truths when they are clearly stated and amply sustained. If motion is the ultimate reality, and space and time are its obverse aspects, all ultimate terms must be made to take their places in this trinity of realities. The word infinite, for instance, can have no signification beyond that of space; and the terms extension, coexistence, and unlimited, so often found in philosophic writings, all stand for the statical aspect of motion, the most convenient name for which is space. On the other hand, the word absolute has no signification beyond that of time, and the terms sequence, invariable fluxion, and unconditioned, mean in their deepest sense the same thing as time. With this understanding of the ultimate significance of the chief philosophic terms, it will be comparatively easy to continue our review of philosophy, for we have the key to every metaphysical situation. CHAPTER II. THE PRE-SOCRATIC PERIOD. Xenophanes-Parmenides-Zeno of Elea-Heraclitus-Anaxagoras-Empedocles-Democritus. ACCORDING to the well-known essay of Victor Cousin, Xenophanes was born in the 40th Olympiad (B.C. 620-616) and must therefore have been the contemporary of Thales. Although he is counted among the early philosophers, he was more a poet than a thinker. He is called the "Rhapsodist of Truth." Banished from his native city, probably on account of his convictions, he wandered over Sicily as a Rhapsodist during the remainder of his life, which lasted nearly a hundred years. His chief aim seems to have been to oppose to the worship of nature and of many gods a pure monotheism, to spread the doctrine of the unity and eternity of God, and to dispel the deep superstitions of his age. Although by no means indifferent to the beauty of the Homeric fables he fiercely opposed the religious falsehood which they contained. Plato, great as was his appreciation of every thing good in literature, took the same position, as can be seen by the latter part of the second and the beginning of the third books of his Republic. In fact, does it not appear as though the criticism of Plato might have been suggested by these verses of Xenophanes ? "Such things of the Gods are related by Homer and Hesiod As would be shame and abiding disgrace to any of mankind; The Rhapsodists were the minstrels of antiquity. They learned poems by heart, and recited them to assembled crowds on the occasions of feasts. In another place the following verse occurs, showing how intimately religious feeling and philosophy were conjoined in the minds of the ancients: "One God, of all things divine and human the greatest, Neither in body alike unto mortals, neither in spirit." Identifying God with the universe-the All-Xenophanes again says: 64 'Wholly unmoved and unmoving, it ever remains in the same place, God moved all finite things; "without labor he ruleth all things by reason and insight." These things sung by a wandering Greek minstrel six hundred years before the beginning of our era, among a people whose only strong bonds of union were connected with religious observances, show how deep-seated are religious feelings, and how much they depend for expression and refinement upon the advance of knowledge. Parmenides, who was born about the 61st Olympiad (B.C. 536), belonged to a wealthy and distinguished family of Elea. It is said that his early life was wasted in dissipation, and that it was only after his friends, Ameinias and Diochætes, had persuaded him to join the Pythagoreans that he embraced a philosophic life and began to contemplate "the bright countenance of Truth in the quiet and still air of delightful studies." Parmenides made a great logical advance on Xenophanes when he warned us that to see Truth we must rely on our reason alone, and not trust our senses, which lead us merely to human Opinion. This discrimination is of much historic interest as it anticipates the doctrine of innate ideas. He believed in the unity of all Being, or, in other words, that all that exists is in its essence the same-the One; that Being alone fills space, while the fullness of all Being is Thought. Non-Being, he assumed, could not be, because nothing can come of nothing. If, therefore, Being |