When Socrates was sixty years old, Plato, then a youth of twenty, came to him as a pupil. When Plato was sixty years old, the seventeen-year-old Aristotle presented himself, joining the Teacher's group of "Friends," as the members of the Academy called themselves. Aristotle was a youth of gentle birth and breeding, his father occupying the position of physician to King Philip of Macedon. Possessed of a strong character, a penetrating intellect, apparent sincerity, but great personal ambition. Aristotle was a student in the Academy during the twenty years he remained in Athens. His remarkable intellectual powers led Plato to call him the "Mind of the School."
After the death of his teacher, Aristotle, accompanied by Xenocrates, went to the court of Hermias, lord of Atarneus, whose sister he afterward married. When Aristotle was forty years old, Philip of Macedon engaged him as tutor for his son Alexander, then thirteen, whose later exploits gained for him the title of Alexander the Great. Philip became so interested in Aristotle that he rebuilt his native city and planned a school where the latter might teach. When Alexander started out to conquer the world, learned men accompanied him to gather scientific facts. After his Persian conquest Alexander presented his former tutor with a sum equivalent to a million dollars, which enabled Aristotle to purchase a large library and continue his work under the most ideal circumstances.
When Aristotle was forty-nine years old he returned to Athens and founded his own school of philosophy. It was known as the Peripatetic School because of Aristotle's habit of strolling up and down the shaded walks around the Lyceum while talking with his pupils. In the morning he gave discourses on philosophy to his more advanced pupils, who were known as his "esoteric" students. In the afternoon a larger circle gathered around him, to whom he imparted simpler teachings. This was known as his exoteric group.
In passing from Plato to Aristotle, we at once become conscious of a distinct change in philosophical concepts and methods. This is all the more noticeable because of our ignorance of Aristotle's complete system. The writings which have come down to us comprise only about a quarter of his works. These are all incomplete, some of them seeming to be notes intended for elaboration in his lectures. They are often sketchy and obscure, highly technical and full of repetitions. Sometimes they are so abstruse that we are obliged to call upon the imagination to supply the missing links of his deductions. Before reaching our Western scholars his works passed through too many hands to remain immaculate. From Theophrastus they passed to Neleus, whose heirs kept them mouldering in subterranean caves for a century and a half. After that his manuscripts were copied and augmented by Apellicon of Theos, who supplied many missing paragraphs, probably from his own conjectures. Although the Arabians were acquainted with Aristotle's...