For Aristotle, the main thing to grasp about a child is what it is not – a creature that has not yet reached the age of reason: childish. But Heraclitus had exploited that ‘deficit’ view of childhood to create characteristic paradoxes in which he exhibits children as however also wiser and sharper than adults. In one of his most enigmatic aphorisms (Fr. 52), he represents the dynamism that propels and sustains us right through life as that of a child at play. After analysis of that paradox and other Heraclitean sayings about children, the chapter turns to Plato’s interest in children and their play, and to his no less paradoxical thesis in the Laws that what, if anything, is truly serious in human life is playful activity, conceived as participation in the ordered play of the gods. We see here an anticipation of Huizinga’s thesis (in Homo Ludens) that in application of the concept of play lies the route to understanding not only children’s games and the place of sport in the lives of adults, but all of what may be regarded as the higher forms of culture, not least law and religious ritual.