Brann, Eva, "Introduction to the Sophist," The Music of the Republic: Essays on Socrates' Conversations and Plato's Writings, Philadelphia: Paul Dry Books, 2011, 278-93.

Excerpt:

The drama of the Sophist is part of a continuing conversation. Three of its participants had talked the day before: Socrates who is known to the world as a philosopher; the brilliant young geometer Theaetetus who so uncannily resembles the ugly Socrates; and Theaetetus’s elderly teacher Theodorus. A young friend of Theaetetus who shares not the looks but the name of the elder Socrates is a silent bystander in both conversation.

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