informal logic also called practical logic, the use of logic to identify, analyze, and evaluate arguments as they occur in contexts of discourse in everyday conversations. In informal logic, arguments are assessed on a case-by-case basis, relative to how the argument was used in a given context to persuade someone to accept the conclusion, or at least to give some reason relevant to accepting the conclusion. See also CIRCULAR REASONING , FORMAL FALLACY , IMPLICATURE , INFORMAL FALLACY , PRAGMATIC CONTRA — DICTION , VALI. D.W.