'Theaetetus is flying': Plato presented the sentence as a paradigm falsehood; good Aristotelians later argued that its falsity was apodictically certain. For the impossibility of human flight seemed to follow ineluctably from two seemingly irrefragable truths. First, there's no flying without wings. 'Flight,' according to Aristotle, 'is the form of locomotion peculiarly appropriate to birds,' and it is properly accomplished by means of wings. (A stock example in the ancient logic books ran: 'If the earth flies, it has wings.') Secondly, men have no wings. According to Aristotle again, 'birds cannot have an upright posture like men. For the nature of their wings is useful to them given the way in which their bodies are in fact constituted, but if they were upright the wings would be useless - as they are on the Cupids which painters depict. And it is clear that no man - nor anything else of a similar form - could be winged: for the possession of wings would be useless for them in their natural movement, and nature makes nothing contrary to nature.' Only things with wings can fly; no man can have wings: therefore no man can fly. Flying is strictly for the birds.

LRB 23 January 1986 | PDF Download