One of the most significant characteristics of a logic based-upon analysis of a language in use is the role of temporal distinctions in the development of rules of discourse. Temporal designations are encountered in the analysis of simple propositions into terms and attributes or relations, and allowance for temporal factors affects rules governing conditions for truth at the propositional level. Temporal considerations also enter into relations between propositions. They are particularly important in the analysis and definition of conditionals. When logic is carried on in a more mathematical artificial language, however, the greater degree of abstraction produces a non-temporal situation. If time conditions are to be noted, they must be reintroduced as special temporal modes.