This chapter argues for the role of collective cognition in creating Roman religious reality. Inauguratio, through which priests were created, was no empty orthopraxic ritual but a means of generating collective belief in order to create socio-religious status and power. Ideally, when Romans judged the ritual of inauguratio efficacious, they collectively believed that Jupiter had sent auspicial signs approving a candidate and that the candidate was therefore a priest. Collective belief was what made the priest a priest, with all the powers and duties concomitant with that status. But the Romans were typically blind to the collective-intentional nature of their social reality. Thus the standard Roman explanation of inauguratio mystifies sacerdotal ontology, holding that priests were priests as a result of Jupiter’s nod. Constitutive beliefs are distinguished from non-constitutive, merely religious beliefs. The Romans’ collectively held constitutive beliefs about sacerdotal status and power actually constituted priests as priests. Although Jupiter’s agency could not be constituted by Roman collective belief, it was a genuine religious belief and part of Roman conceptions of the basis of sacerdotal authority.