The paper aims to overview some typical principles of communicative language use in a cognitive pragmatic approach applying a reductionist method in order to demonstrate that the well-known principles can be reduced to a very general rationality (economy) principle. After briefly reviewing the principles the paper re-evaluates them and provides a new classification of them relying on the definition of ostensive-inferential communication. The principles which can be divided into rationality and interpersonality principles are really principles of effective information transmission on objects and selves. They refer to two kinds of language use: informative and communicative ones. The only principles valid for only communicative language use are the communicative principle of relevance and the principle of communicative intention suggested in the present article. Finally, the paper reduces all rationality and interpersonality principles to a very general rationality principle, i.e., the cognitive principle of relevance.