In A Social Ontology of Psychosis, Diego Enrique Londoño-Paredes explores how to interpret and apply the concept of the signifier of the Name-of-the-Father in Lacanian theory, particularly in the context of working with psychosis.Londoño proposes a logical framework drawing on the work of Badiou, then traces the historical development of this concept and its implications as a structural necessity for anyone who speaks and engages in discourse. The book opens by exploring set theory, transitioning from nought to one, from the Thing to the object, essential for any presentation. Subsequently, it follows a historical path, examining the evolution of the figure and the signifier of the Father, journeying from ancient Mesopotamian roots through Modernity, touching upon Claudel's theater and the films of the Coen brothers. Finally, it aligns Searle's social ontology with Lacan's discourses, highlighting psychosis as an illustration of being outside discourse, particularly when the Name-of-the-Father is foreclosed. Case material illustrates various ways psychosis manifests without distinct clinical evidence.This comprehensive book will be of great interest to practitioners and scholars in psychoanalysis, philosophy, the humanities, and the history of mental health and knowledge.