 Our earliest extant source—and the only one who can claim to have known Socrates in vigorous midlife—is the playwright Aristophanes. His comedy, Clouds, was produced within a year of the battle of Delium (423) at which Socrates fought as a hoplite, and when both Xenophon and Plato were infants. In the play, the character called Socrates heads a Think-o-Rama in which young men study the natural world, from insects to stars, and study slick argumentative techniques as well, lacking all respect for the Athenian sense of propriety. The actor wearing the mask of Socrates makes fun of the traditional gods of Athens (lines 247–48, 367, 423–24), mimicked later by the young protagonist, and gives naturalistic explanations of phenomena Athenians viewed as divinely directed (lines 227–33; cf. Theaetetus 152e, 153c–d, 173e–174a; Phaedo 96a–100a). Worst of all, he teaches dishonest techniques for avoiding repayment of debt (lines 1214–1302) and encourages young men to beat their parents into submission (lines 1408–46).