Philosophy can be described as a historical discipline subject to change over time. The pre-Socratic epoch represents the birth of Western philosophical speculation in the greater Greek diaspora. Classical Greek philosophers such as Socrates, Plato, and Aristotle drew on the pre-Socratic traditions, as well as on one another's teachings, to construct the first full-blown philosophical systems. The Hellenic and Roman worlds inherited these classical doctrines and incorporated them into their own philosophic perspectives.