Abstract: Classic pragmatic theories such as principle of rationality， relevance theory and Face theory all claim that language use is rational. However， this proposition can be falsified via an analysis of two key notions， namely， rationality and act of language use. The distinction between non-rationality and irrationality helps define rationality-n and rationality-i. The act of language use is rational-n， but not necessarily rational-i. Structurally， the act of language use can be divided into strategic act and verbal act. In terms of Max Weber's taxonomy of social acts， both strategic and verbal acts can be one or a combination of two or more types of the four social acts， namely， instrumentally rational act， value-rational act， affectual act， and traditional act. Therefore， the act of language use can be either rational-i or irrational.

Key words: rationality-n, rationality-i, act of language use, strategic act, verbal act