Introduction: Delusions are commonly defined as beliefs and are evaluated in terms of truth and falsehood. However, there are many conceptual, empirical and pragmatic problems derived from this characterization Method: Beliefs, knowledge, and Wittgenstein's certainties of a world-picture, religious beliefs, and political, ethical, and esthetic ideas were evaluated, finding that delusions are different from all of these. To understand what delusions are, the language used to express in first-person what we experience of ourselves and during interactions with others is examined. It is not the language of psychology as a discipline which is, after all, in the third-person, but phrases, sentences and narratives uttered by a subject that renders his view of what he perceives, feels and thinks. Conclusion: Delusions are not beliefs. They are verbal expressions of anomalous experiences connected to somatic perceptions, emotions related to interactions with other human beings, and emotions related to the manner in which we are in the world.