What is rationality? Rationality is the quality or state of being reasonable, based on facts or reason. Rationality has different meanings in different branches of studies like sociology or psychology. Rationality has been the focal point of research by philosophers as well as social scientists. Many sociologists believe that rationality along the lines of rational choice theory is not a useful concept for understanding human behavior.
The background assumptions are the model within which rationality applies. When making a decision rationality factors in how much information is available. A rationality model in which benefitting oneself is optimal then it is equated with self-interest. A rationality model in which benefiting the group is optimal then purely selfish behavior is deemed irrational.
Max Weber proposed an interpretation of social action that proposed four idealized types of rationality. The first type, Max Weber called instrumental rationality, is related to the expectations about the behavior of other human beings or objects, rationally pursued and calculated. The second type, Max Weber called value-oriented or belief-oriented undertaken for what one might call reasons intrinsic to the actor, ethical or aesthetic. The third type, Max Weber called affectual, determined by an actor's specific affect, feeling, or emotion. The fourth type, Max Weber called conventional, determined by ingrained habituation.
According to Ayn Rand, rationality is the recognition of the fact that existence exists, that nothing can alter the truth and nothing can take precedence over that act of perceiving it, that reason is an absolute that permits no compromise. Rationality is man’s basic virtue, the source of all his other virtues. The virtue of Rationality means the recognition and acceptance of reason as one’s only source of knowledge, one’s only judge of values and one’s only guide to action.