||In the late 19th and early 20th Century, many psychologists posited group minds to explain the behavior of crowds and states, as well as the emergence of norms and societal facts. In a world populated by powerful labor unions, anarchist collectives, and radical workers’ parties, each resisting the unfair demands of powerful corporate agents, it seemed reasonable to assume that powerful psychological forces were at play in the production of collective behavior. But these theories of collective mentality relied on such implausibly weak forms of functionalism and such excessively inflationary ontologies that they shared little in common with the theories of mental states that emerged in other parts of philosophy and the cognitive sciences. In the current age of popular uprisings, failing political parties, and increasing corporate power, it come s as no surprise that philosophers, psychologists, and cognitive scientists have once again developed an interest in collective behavior. A number of popular books have attempted to resuscitate claims about collective intelligence and collective decision-making; and there is a rapidly growing philosophical literature on issues of collaboration, collective intentionality, collective decision-making, and collective responsibility. Research on collective mentality spans a wide range of philosophical topics that pertaining to group minds and collective mental states. Like the philosophy of mind more broadly, the investigation of collective mentality overlaps in rich and important ways with the philosophy of action and the philosophy of cognitive science. On the one hand, there is a long tradition of analyzing the nature and possibility of collective intentionality (this research is mainly catalogued under the 'collective action', 'collective intentionality', and 'collective responsibility' subcategories). On the other hand, there is a more recent field of investigation, grounded in the scientific study of distributed cognition. This research has targeted everything from issues of cognitive architecture, to questions about the possibility of collective consciousness and the possibility of collective mental representation.