From Citizendium, the Citizens' Compendium
Ancient philosophy refers to philosophy produced during the ancient period, which includes the ancient Greek and Roman civilisations and is usually thought to end with Augustine. The three towering figures of ancient philosophy are the Athenians Socrates, Plato and Aristotle. But before Socrates, there were plenty of other philosophers. Some consider Thales the father of Western philosophy, while some see Zarathustra, the founder of Zoroastrianism to be both the founder of philosophy and monotheistic religion alike.
Unlike the scientific and academic world of today, there was very little disciplinary subdivision - philosophers of the ancient world were also theologians, lawyers, teachers, scientific investigators, mathematicians and producers of literature. Aristotle, as well as being a philosopher, is known both for metaphysical and ethical philosophy, but also for producing formal logic, for putting forward theories in what would today be called physics, and for studying and starting biology and zoology as a field.
While Western philosophy has tended towards significantly more logical rigor in the last century, study of the works of the ancient originators of the subject remain a core part of the training of any philosopher. Many of the problems which originate in the dialogues of Socrates and Plato and in the more systematic thought of Aristotle haunt philosophy continuously. These questions inevitably get modified to take account of the religious, scientific or political context of the day: questions regarding the Forms described by Plato in the Phaedo, Republic and Phaedrus are still discussed, but often today with the relationship of our common language to the objects posited by astrophysicists (see scientific realism), while questions of ethics and justice are tested against contemporary ethical problems raised by genetic engineering, embryological research, in-vitro fertilisation and the knowledge given to us by our understanding of DNA. Alfred North Whitehead in Process and Reality described the tradition of Western philosophy as being a "series of footnotes to Plato". Bernard Williams claimed that the "legacy of Greece to Western philosophy is Western philosophy".
A number of post-Aristotelian philosophical schools also attempted to live the philosophies they propounded: the Stoics, the Epicureans, the Cynics and the Sceptics. Much of this philosophy is still seen today as giving practical advice for living: Marcus Aurelius' Meditations is popular today and often prescribed as a source of practical wisdom; the allegorical and lyrical Consolation of Philosophy by Boethius falls slightly outside of most people's boundaries of ancient philosophy (Dante in The Divine Comedy excepted), but does provide similarly practical philosophy combining, as it does, Neoplatonism and the ethics of Christianity.
Ancient philosophy is often subdivided into a number of categories: the Pre-Socratic era, the Socratic era, the post-Aristotelian Hellenistic era and the Roman philosophers. Before Socrates, philosophers of interest included Thales, Democritus, Leucippus Heraclitus, Anaximander, Zeno and Parmenides. The Sophists - Gorgias, Cratylus, Antiphon, Thrasymachus etc. - often appear in Plato's Socratic dialogues.