This paper is about rational and irrational uses of deontological words, such as “should”, “ought”, and “must”, referred to as “the shoulds”. Rationality is taken as a mutual relationship between conceptual schemes and human agency. These are expressed in what Bakhtin referred to as authoritative discourse and internally persuasive discourse respectively. When the conceptual scheme is in place and its authority transparent, and there is interplay between authoritative discourse and internally persuasive discourse, then the shoulds are perceived as rational. When (...) the interplay is disrupted or suppressed the shoulds are seen as irrational. Breakdown occurs in two main ways. First, when the effective conceptual schemes are hidden, and the origin of the shoulds obscured. We describe some instances of the latter, from philosophy, psychotherapy, and experimental studies of rationality. Second, in technology and science the mutual relationship sometimes breaks down because authoritative discourse is too powerful, and inhibits the interplay in order to maintain itself. After describing these pathologies, we turn to William James, who drew attention to a repair kit for rationality in his detection of the psychologist's fallacy. Describing the work of Dewey and Husserl as elaborations of this, we distinguished two essential aspects of rationality, disciplinary expressed in authoritative discourse, and emancipatory expressed in internally persuasive discourse. (shrink)