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Since concepts, in the field of cognition, perform a function similar to that of numbers in the field of mathematics, the function of a proposition is similar to that of an equation: it applies conceptual abstractions to a specific problem.

A proposition, however, can perform this function only if the concepts of which it is composed have precisely defined meanings. If, in the field of mathematics, numbers had no fixed, firm values, if they were mere approximations determined by the mood of their users — so that “5,” for instance, could mean five in some calculations, but six-and-a-half or four-and-three-quarters in others, according to the users’ “convenience”—there would be no such thing as the science of mathematics.

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