Note 405 — Part I.—Experience

"The definition above given of a triangle obviously comprises not one, but two propositions, perfectly distinguishable. The one is, 'There may exist a figure bounded by three straight lines the other. 'And this figure may be termed a triangle.' The former of these propositions is not a definition at all; the latter is a mere nominal definition, or explanation of the use and application of a term. The first is susceptible of truth or falsehoods, and may therefore be made the foundation of a train of reasoning. The latter can neither be true nor false; the only character it is susceptible of is that of conformity to the ordinary usage of language."—Mill's "Logic," I. 162.