These sentences [of Plato] contain the culture of nations; these are the corner-stone of schools; these are the fountain-head of literatures. A discipline it is in logic, arithmetic, taste, symmetry, poetry, language, rhetoric, ontology, morals, or practical wisdom. There never was such a range of speculation. Out of Plato come all things that are still written and debated among men of thought. Great havoc makes he among our originalities. We have reached the mountain from which all these drift-bowlders were detached.... Plato, in Egypt and in Eastern pilgrimages, imbibed the idea of one Deity, in which all things are absorbed. The unity of Asia and the detail of Europe, the infinitude of the Asiatic soul and the defining, result-loving, machine-making, surface-seeking, opera-going Europe Plato came to join, and by contact to enhance the energy of each. The excellence of Europe and Asia is in his brain. Metaphysics and natural philosophy expressed the genius of Europe; he substricts the religion of Asia as the base. In short, a balanced soul was born, perceptive of the two elements.... The physical philosophers had sketched each his theory of the world; the theory of atoms, of fire, of flux, of spirit,--theories mechanical and chemical in their genius. Plato, a master of mathematics, studious of all natural laws and causes, feels these, as second causes, to be no theories of the world, but bare inventories and lists. To the study of Nature he therefore prefixes the dogma,--'Let us declare the cause which led the Supreme Ordainer to produce and compose the universe. He was good; ... he wished that all things should be as much as possible like himself.'...
Plato ... represents the privilege of the intellect,--the power, namely, of carrying up every fact to successive platforms, and so disclosing in every fact a germ of expansion.... These expansions, or extensions, consist in continuing the spiritual sight where the horizon falls on our natural vision, and by this second sight discovering the long lines of law which shoot in every direction.... His definition of ideas as what is simple, permanent, uniform, and self-existent, forever discriminating them from the notions of the understanding, marks an era in the world.
The great disciple of Plato was Aristotle, and he carried on the philosophical movement which Socrates had started to the highest limit that it ever reached in the ancient world. He was born at Stagira, 384 B.C., and early evinced an insatiable thirst for knowledge. When Plato returned from Sicily Aristotle joined his disciples at Athens, and was his pupil for seventeen years. On the death of Plato, he went on his travels and became the tutor of Alexander the Great, and in 335 B.C. returned to Athens after an absence of twelve years, and set up a school in the Lyceum. He taught while walking up and down the shady paths which surrounded it, from which habit he obtained the name of the Peripatetic, which has clung to his name and philosophy. His school had a great celebrity, and from it proceeded illustrious philosophers, statesmen, historians, and orators. Aristotle taught for thirteen years, during which time he composed most of his greater works. He not only wrote on dialectics and logic, but also on physics in its various departments. His work on "The History of Animals" was deemed so important that his royal pupil Alexander presented him with eight hundred talents--an enormous sum--for the collection of materials. He also wrote on ethics and politics, history and rhetoric,--pouring out letters, poems, and speeches, three-fourths of which are lost. He was one of the most voluminous writers of antiquity, and probably is the most learned man whose writings have come down to us. Nor has any one of the ancients exercised upon the thinking of succeeding ages so wide an influence. He was an oracle until the revival of learning. Hegel says:--
"Aristotle penetrated into the whole mass, into every department of the universe of things, and subjected to the comprehension its scattered wealth; and the greater number of the philosophical sciences owe to him their separation and commencement."
He is also the father of the history of philosophy, since he gives an historical review of the way in which the subject has been hitherto treated by the earlier philosophers. Says Adolph Stahr:--
"Plato made the external world the region of the incomplete and bad, of the contradictory and the false, and recognized absolute truth only in the eternal immutable ideas. Aristotle laid down the proposition that the idea, which cannot of itself fashion itself into reality, is powerless, and has only a potential existence; and that it becomes a living reality only by realizing itself in a creative manner by means of its own energy."
There can be no doubt as to Aristotle's marvellous power of systematizing. Collecting together all the results of ancient speculation, he so combined them into a co-ordinate system that for a thousand years he reigned supreme in the schools. From a literary point of view, Plato was doubtless his superior; but Plato was a poet, making philosophy divine and musical, while Aristotle's investigations spread over a far wider range. He differed from Plato chiefly in relation to the doctrine of ideas, without however resolving the difficulty which divided them. As he made matter to be the eternal ground of phenomena, he reduced the notion of it to a precision it never before enjoyed, and established thereby a necessary element in human science. But being bound to matter, he did not soar, as Plato did, into the higher regions of speculation; nor did he entertain as lofty views of God or of immortality. Neither did he have as high an ideal of human life; his definition of the highest good was a perfect practical activity in a perfect life.
With Aristotle closed the great Socratic movement in the history of speculation. When Socrates appeared there was a general prevalence of scepticism, arising from the unsatisfactory speculations respecting Nature. He removed this scepticism by inventing a new method of investigation, and by withdrawing the mind from the contemplation of Nature to the study of man himself. He bade men to look inward. Plato accepted his method, but applied it more universally. Like Socrates, however, ethics were the great subject of his inquiries, to which physics were only subordinate. The problem he sought to solve was the way to live like the Deity; he would contemplate truth as the great aim of life. With Aristotle, ethics formed only one branch of attention; his main inquiries were in reference to physics and metaphysics. He thus, by bringing these into the region of inquiry, paved the way for a new epoch of scepticism.
Both Plato and Aristotle taught that reason alone can form science; but, as we have said, Aristotle differed from his master respecting the theory of ideas. He did not deny to ideas a subjective existence, but he did deny that they have an objective existence. He maintained that individual things alone exist; and if individuals alone exist, they can be known only by sensation. Sensation thus becomes the basis of knowledge. Plato made reason the basis of knowledge, but Aristotle made experience that basis. Plato directed man to the contemplation of Ideas; Aristotle, to the observation of Nature. Instead of proceeding synthetically and dialectically like Plato, he pursues an analytic course. His method is hence inductive,--the derivation of certain principles from a sum of given facts and phenomena. It would seem that positive science began with Aristotle, since he maintained that experience furnishes the principles of every science; but while his conception was just, there was not at that time a sufficient amount of experience from which to generalize with effect. It is only a most extensive and exhaustive examination of the accuracy of a proposition which will warrant secure reasoning upon it. Aristotle reasoned without sufficient certainty of the major premise of his syllogisms.
Aristotle was the father of logic, and Hegel and Kant think there has been no improvement upon it since his day. This became to him the real organon of science. "He supposed it was not merely the instrument of thought, but the instrument of investigation." Hence it was futile for purposes of discovery, although important to aid processes of thought. Induction and syllogism are the two great features of his system of logic. The one sets out from particulars already known to arrive at a conclusion; the other sets out from some general principle to arrive at particulars. The latter more particularly characterized his logic, which he presented in sixteen forms, the whole evincing much ingenuity and skill in construction, and presenting at the same time a useful dialectical exercise. This syllogistic process of reasoning would be incontrovertible, if the general were better known than the particular; but it is only by induction, which proceeds from the world of experience, that we reach the higher world of cognition. Thus Aristotle made speculation subordinate to logical distinctions, and his system, when carried out by the mediaeval Schoolmen, led to a spirit of useless quibbling. Instead of interrogating Nature they interrogated their own minds, and no great discoveries were made. From want of proper knowledge of the conditions of scientific inquiry, the method of Aristotle became fruitless for him; but it was the key by which future investigators were enabled to classify and utilize their vastly greater collection of facts and materials.