Abstract

The first solid bit of argumentation you get in Plato's Phaedo goes something like this: Whatever comes to be, comes to be from its opposite . If at a certain time t a given thing a begins to be F , before that time t it must have been non- F . Wherever a pair of predicates, F and G , are genuine contradictories; where, that is, they stand to each other in the same relation as F stands in to non- F ; it is necessarily true that if a began to be F at t before then a was G . The only trouble comes from the difficulty of finding substitutes for F and G that people will allow to be genuine contradictories. It the butter began to be soft at four o'clock, we may suggest, before four it was hard. A tiresome opponent will retort that there is a state in which butter cannot properly be called either hard or soft. We try again: If Ann began to be asleep at eight, before eight she was awake; if my shirt became dirty on Tuesday, before Tuesday it was clean; if Bonzo died last week, before last week he was alive. And when the advocate of the borderline state reminds us of the various twilight areas of consciousness or cleanliness, we are reduced to legislation: “asleep” shall henceforth apply to every mental state short of complete wakefulness, “alive” to every condition of the body before the onset of putrefaction, “clean” to every shirt incapable of producing a certain measurable discoloration in the water in which it is washed. “Let F and G be contradictories”, we still guardedly maintain: “then if a comes to be F at time t , before time t a was G ”