The transition from a vague generalization to an accurate statement is the first step on the road to science. It is a step of great importance. Vague generalizations find a ready entrance into many minds, and produce a comfortable sense of satisfaction that is easily mistaken for knowledge, and that stops further questioning. An exact statement of fact, on the other hand, draws attention to detail, and shows itself to be set in a mass of further detail that it challenges you to explore. “Nature abhors a vacuum” sounds final; it explains why water will rise in an ordinary suction-pump rather than allow a vacuum to be produced; why the schoolboy’s “sucker” will lift a stone; and many other phenomena of a similar kind. It explains everything by a phrase and stimulates no inquiry. But when Galileo noted that the pump would raise water only to a height of about 32 feet, and pointed out that this gives a measure of the extent to which Nature abhors a vacuum in its dealings with water, new questions arose, stimulating further investigation.