Informal Logic and Logic

Abstract

This chapter examines some of the features of the relation between informal logic and logic. Informal logic originated with the rejection of the use of formal logic for the purpose of the analysis and the evaluation of natural language discursive arguments. While not a rejection of formal logic, this declaration of independence required those who identified theoretically with the informal logic critique of formal logic’s usefulness for this purpose to look elsewhere for analytic and normative tools. One of these was the theory of the informal fallacies. Another is to regard the acceptability of premises and the relevance and sufficiency of the premise-conclusion link as the informal criteria of a logically good argument. A third is the use of argument scheme theory. Argument scheme analysis and critique, while informal, has been used in Artificial Intelligence to develop computer programs to analyze, assess and even construct arguments in natural language. Since computer programs require necessary relations between premises and conclusions, that is, the deductive validity that characterizes formal logic, it seems that at present informal and formal logic have come together.