Speusippus Analysis


Speusippus (spyew-SIHP-uhs), an Athenian, was the son of Eurymedon and Plato’s sister Potone. He probably entered Plato’s Academy when it was founded and is known to have traveled with Plato to Sicily in 361 b.c.e. After Plato’s death, he became head of the Academy, a position he held until his own death. Little else is known about his life.


In the ancient world, Speusippus was known for having written a number of books on philosophy, of which only fragments remain. He disagreed with Plato on a number of points, such as the nature of pleasure (which he regarded as an evil), definition (which he regarded as impossible without knowledge of all that exists), and the forms (whose existence he denied). Although it is speculative, it seems likely that he criticized Plato using the notorious “Third Man” argument (infinite regression). He in turn was criticized by Aristotle because he believed in a strict separation of different kinds of reality (such as sensible things and numbers). Aristotle likened this to a bad tragedy, saying that nature is not constructed from disconnected episodes.

Additional Resources

Dancy, R. M. “Ancient Non-Beings: Speusippus and Others.” Ancient Philosophy 9 (1989): 207-243.

Dancy, R. M. Two Studies in the Early Academy. Albany, N.Y.: State University of New York Press, 1997.

Guthrie, W. K. C. A History of Greek Philosophy. 6 vols. New York: Cambridge University Press, 1978-1990.

Taran, Leonardo. Speusippus of Athens: A Critical Study with a Collection of the Related Texts and Commentary. Leiden, Netherlands: E. J. Brill, 1981.