How is it that little children are so intelligent and men so stupid? It must be education that does it.

The remark is a sardonic inversion of the usual assumption that education refines and improves. By contrasting the quick, candid intelligence often observed in children with the dullness or complacency of adults, the speaker implies that formal schooling and social “education” can train people out of curiosity, spontaneity, and independent judgment. The line works as social satire: it targets not learning itself but the ways institutions, conventions, and rote instruction can produce conformity and intellectual timidity. Its punch depends on paradox—education, meant to enlighten, is blamed for making people stupid—inviting readers to distinguish genuine understanding from mere credentialed training.