Sometimes historians treat science studied in the past as if it was discovered today. They seem to forget that words mean different things in different times, and evaluate definitions and proofs according to the modern standards of rigor. Kenneth O. May assigns this mistake to the beginner: "The amateur historian examines a mathematical paper of the past as if its author were taking an examination in mathematics today and amuses himself by finding "errors'. Or he may force the ideas of one period into an inappropriate framework of another."¹