Ancient philosophy (c. 600 B.C.–c. A.D. 500)

Ancient philosophy is the philosophy of the Graeco-Roman world from the sixth century [circa 585] B.C. to the fourth century A.D. It is usually divided into four periods: the pre-Socratic period, the periods of Plato and Aristotle, and the post-Aristotelian (or Hellenistic) period. Sometimes a fifth period is added that includes the Christian and Neo-Platonist philosophers. The most important of the ancient philosophers (in terms of subsequent influence) are Plato and Aristotle.

The themes of ancient philosophy are: understanding the fundamental causes and principles of the universe; explaining it in an economical and uniform way; the epistemological problem of reconciling the diversity and change of the natural universe, with the possibility of obtaining fixed and certain knowledge about it; questions about things which cannot be perceived by the senses, such as numbers, elements, universals, and gods; the analysis of patterns of reasoning and argument; the nature of the good life and the importance of understanding and knowledge in order to pursue it; the explication of the concept of justice, and its relation to various political systems.

In this period the crucial features of the philosophical method were established: a critical approach to received or established views, and the appeal to reason and argumentation.