Tautologies in Economics and the Natural Sciences

Propositions true by interlocking definitions or by convention occur fairly often. Recognizing their nature and usefulness helps forestall misunderstanding and quibbles. Examples include Walras's Law, the equation of exchange, microeconomic tautologies, the money-multiplier formula, the government budget constraint, the principle of comparative advantage, and certain strands of balance-of -payments analysis. Comparisons are drawn with examples from mathematics, classical mechanics, electricity, and other fields.