Much contemporary research in philosophy and related fields attempts to explain cognitive phenomena that are significantly deviant from standard norms of rationality. Delusions, self-deception, wishful thinking, confabulations, and feigning memories, are pervasive in human reasoning, undermining the very idea of the subject as a rational agent. This conference aims at discussing the nature, formation processes, and epistemic role of irrational phenomena in human cognition, by promoting an interdisciplinary discussion of rationality and its ‘rivals’.