Stoic Six Pack 7 Ð The Sophists brings key primary and secondary sources together in one volume for a fully rounded understanding of this early, often misunderstood philosophical movement: The Sophists by Henry Sidgwick; Protagoras, Euthydemus and Gorgias by Plato; Memoirs of Socrates by Xenophon; Stoic Self-control by William De Witt Hyde and The Sophists Ð Biographical Sketches by William Smith.