dialecticians have always turned their sharpest weapons. It has again and again been dissected and refuted and shown to be philosophically untenable: but it still lives and has still something of the old power to shatter and to set free. All the thinkers of Greece at the time we are treating were testing the laws and maxims of their day, and trying to find out what really rested on Nature and what was the mere embroidery of man. It is always a dangerous and exciting inquiry; especially because the most irrational conventions are apt also to be the most sacrosanct.
This whole spirit was specially incarnate in another of Euripides' teachers. We hear of Protagoras in his old age from that enemy of the sophists, Plato. But for this sophist even Plato's satire is kindly and almost reverent. Protagoras worked not at physical science, but at language and philosophy. He taught men to think and speak; he began the study of grammar by dividing sentences into four kinds, Optative, Interrogative, Indicative, Imperative. He taught rhetoric; he formulated the first theory of democracy. But it was as a sceptic that he struck men's imaginations most. "About the Gods, I have no means of knowing either that they are or
