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Xenocrates (396-314 BCE)

Greek philosopher who defended the philosophy of Plato against the criticism of Aristotle. As head of the Academy in the fourth century, Xenocrates held forth the quasi-Pythagorean view that the Platonic Forms, including even the individual human soul, are all numbers.

Also see SEP, EB, and ELC.

Xenophanes of Colophon (570-475 BCE)

Presocratic philosopher. He criticized the militarism and anthropomorphism of traditional Greek morality and religion, arguing that fundamental truth about the world is difficult to achieve. His opposition to conventional notions earned him the respect of later, more completely skeptical thinkers. Parmenides and Zeno studied with Xenophanes in Sicily before establishing their own school at Elea.

Recommended Reading: Xenophanes of Colophon: Fragments, tr. by J. H. Lesher (Toronto, 1992).

Also see SEP, IEP, EB, and ELC.

Xenophon (430-350 B.C.E.)

Greek historian. Xenophon's dialogues, especially the Απολογημα (Apology) and Memorabilia, offer an account of the philosophical career of Socrates through more practical, worldly eyes than do the dialogues of Plato.

Recommended Reading: Xenophon: Memorabilia, Oeconomicus, Symposium, Apologia, tr. by E. C. Marchant and O. J. Todd (Harvard, 1923); Xenophon, Conversations of Socrates, tr. by Hugh Tredennick (Penguin, 1990); and Leo Strauss, Xenophon's Socrates (St. Augustine, 1997).

Also see IEP, EB, and ELC.


German term for time; thus die Zeitgeist, or "Spirit of the Age" is the set of conceptions characteristic of the thinkers of a particular era.

Zeno of Citium (334-262 BCE)
Zeno of Citium

Greek philosopher. An early exponent of stoic philosophy, he devised its characteristic separation of logic, natural science, and ethics. According to Zeno, only acceptance of objective reality permits human beings to overcome their subjective passions.

Recommended Reading: Edwyn Bevan, Stoics and Skeptics (Ares, 1980).

Also see Larnaca, Cyprus, EB, and ELC.

Zeno of Elea (c. 450 BCE)
Zeno of Elea

Follower of Parmenides whose work is known to us only through fragmentary reports from other philosophers. Zeno was the presocratic philosopher who devised clever paradoxes to show that motion of any kind is impossible and that reality must be unitary and unchanging.

Recommended Reading: J. A. Farris, The Paradoxes of Zeno (Avebury, 1996) and Zeno's Paradoxes, ed. by Wesley C. Salmon (Hackett, 2001).

Also see SEP on Zeno and the paradoxes, IEP, John Burnet, MMT, EB, ELC, and CE.

Zermelo, Ernst Friedrich Ferdinand (1871-1953)

German mathematician who developed the first systematic axiomatization of set theory. This achievement drew attention to the importance of the axiom of choice.

Recommended Reading: Gregory H. Moore, Zermelo's Axiom of Choice: Its Origins, Development, and Influence (Springer Verlag, 1988).

Also see MMT and WSB.


In contemporary discussions of the philosophy of mind, a hypothetical being whose appearance, behavior, and speech is indistinguishible from that of a normal human being despite its total lack of conscious experience in any form.

Recommended Reading: Daniel C. Dennett, Consciousness Explained (Little, Brown, 1992) and The Nature of Consciousness: Philosophical Debates, ed. by Ned Block and Owen Flanagan (MIT, 1997).

Also see SEP and DPM.


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Last modified 31 December 2011.
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