Every individual, from the common mechanic, that works in wood or clay, to the prime minister that regulates with the dash of his pen the agriculture, the breeding of cattle, the mining, or the commerce of a nation, will perform his business the better, the better he understands the nature of things, and the more his understanding is enlightened.

Book III, On Consumption, Chapter VI, Section II, p. 432 - A Treatise On Political Economy (Fourth Edition) (1832)