Plato (c. 427-c. 347 BCE)

Along with his teacher Socrates and his pupil Aristotle, Plato is recognized as one of the most influential thinkers in ancient philosophy. Plato deals with the notion of time in different contexts. He describes time as “a moving image of eternity” in his philosophy of nature (in his Timaeus, 37c-47c): the temporal structure of the cosmic universe aims at imitating the unchangeable eternal realm of the ideas, of which the real world is a reflection. Plato also develops (in the dialogue the [Page 1015]Statesman I the Politikos, 268d-274d) the idea of a cyclic dimension of the historical time, which consists of two “world ages” that alternate for eternity. The two ages have different characteristics and are seen as a result of a change of the overall inner motion of the cosmos. Finally, Plato aims at a deeper understanding of the paradoxes of movement that are linked to temporal becoming (in the dialogue Parmenides, 151e-157b). The main background for Plato's understanding of time is his doctrine of ideas, according to which the temporal world is in constant change; but “behind” this change lies the realm of unchangeable ideas, which exists outside of space and time.

Born in Athens, Greece, into an old aristocratic family, Plato was hindered in his pursuit of a political career by the turbulent politics of his times. In his youth he was a pupil of Socrates for 8 years, until Socrates' trial and execution in 399 BCE. After the death of Socrates, Plato's extended travels led him to Cyrene and Egypt and thus to Euclid of Megara, then to lower Italy, and to the Pythagoreans. In 385 Plato founded his famous school, the academy in Athens (which was only to be closed in 529 CE). He traveled several times to Sicily, where he attempted to put his political ideas into practice. He discarded this, however, after he fell into disgrace, became enslaved, and had to be redeemed by his pupils.

The platonic works that are preserved—besides the letters and the Apology—are all written in the form of dialogues, most of which depict Socrates debating with his interlocutors to seek the truth. Socrates' quest for a deeper understanding of the virtues and the nature of the good is presented as an antidote to the relativism and the empty rhetoric of the Sophists. In Epistemology, Plato aims thus at a distinction between true knowledge (episteme) and mere belief (doxa). In his political works he depicts a perfect state that is described as a corporate state, in which the people with the highest wisdom—the philosophers—should rule. Most influential for western metaphysics was Plato's doctrine of ideas, which also serves as a background for his cosmological notion of time.