Why is the dialogue among professionals who adopt different perspectives regarding psychopathology so difficult? In this article, we point out that the way we justify the knowledge we use influences to what extent we are open to dialogue. We believe that Cartesian foundationalism, broadly used in psychopathology and in science in general, fosters the appearance and maintenance of sectarianisms that exclude alterity. As a main alternative to foundationalism one can adopt coherentism as a justification for knowledge. This conception is based on the idea that truth is never definite, and that the validity of an item of knowledge occurs through its relation to other items. We present the concept of dialogue of Gadamer’s philosophical hermeneutics, because, as we believe, the adoption of this concept can contribute to a better interaction between professionals. In conclusion, we emphasize the importance of pluralism as an alternative to the imposition of power and authority.