Aristotle was born in 384 BC in a small town called Stagira (modern day Stavró), located on the northern coast of the Aegean Sea. His father, Nicomachus, was a physician, a member of the guild of the Asclepiadæ, and his mother was Phæstis from Chalcis. Nicomachus had served as the court physician under Amyntass II of Macedonia, and this connection would later help lead to Aristotle's tutorship of Alexander the Great. Aristotle's parents died early, and he was raised by a guardian named Proxenus. Nevertheless, it is possible to find some traces of Nicomachus's early influence on Aristotle's development. The philosophic tradition in Greece at this time was still shaky, with no grounding in a scientific method. On the other hand, there is strong evidence for the employment of such methods in medical science, where observation preceded prognosis. This discipline no doubt revealed itself in Aristotle's later tendencies. Moreover, his interest in medicine and especially biology can be traced back to his early exposure. Asclepiad families are thought to have trained their sons in dissection, and Aristotle would likely have received this training; he may even have helped his father during surgical procedures.
Little is known about Aristotle's life before he entered Plato's Academy at the age of eighteen. The choice was probably not out of some burning desire for philosophical knowledge, but rather a simple recognition that the best education offered in Greece lay there. There was no doubt in anyone's mind that Aristotle was Plato's best pupil, called "the mind of the school" by Plato himself. Nevertheless, it might seem surprising that two of the most powerful minds in human history remained together for approximately twenty years despite the fundamental differences between them. But while Aristotle could not accept Plato's doctrines without debate, Platp laid the groundwork for all of Aristotle's future philosophical (though not his scientific) works. Aristotle was always careful to emphasize the common principles that bound his philosophy to Plato's, despite the objections he raised, and he always spoke of Plato's Academy with fondness.
During this time, Aristotle may also have begun some scientific research, though no one at the school could have given him much guidance beyond a certain point. He also may have lectured but most likely only on rhetoric. From this period several of his writings were lost, most likely ones pertaining to philosophical theories that were not particularly original. When Plato died in 347, he was succeeded by his nephew Speusippus, who stood for components of the Academy that Aristotle particularly disliked, especially the tendency to turn philosophy into mathematics. This development, along with the anti-Macedonian sentiment growing in Athens, probably led to Aristotle's departure. He left with his Academy colleague Xenocrates to spend some time with a former fellow-student named Hermeias, who had risen from the status of a slave to become the ruler of Atarneus and Assos. There he remained for three years, marrying Hermeias's niece and adopted daughter Pythias. Pythias bore him a daughter of the same name and died shortly after. Later Aristotle would enter into an unofficial but lasting union with Herpyllis, a native of Stagira, and with her he would have a son named Nicomachus.