Science, language, and logic are interlocking concepts in Hobbes’s philosophy. Science is a set of true sentences or propositions of a language. It consists of two parts. The first part is a set of definitions, which are in effect axioms (cf. DCo 3.9). The second part is all of the sentences that are entailed by those definitions either directly or indirectly (cf. Hanson 1990). The inferences from definitions or from intermediate sentences (theorems) to other theorems are calculations or reckonings of words, just as adding and subtracting numbers are. The calculation of words is reasoning (L 5.2); the study of reasoning is logic. Science, language, and logic, then, form a tight cluster of concepts.