The present chapter is about the adaptive functions of Inquisitions as ultrasocial institutions. As reflected by the quote above from one of the New Testament Epistles of the Apostle Paul, we advance the proposition that so-called “heretics” are investigated and persecuted for the purpose of reinforcing the political, social, and cultural bonds among the so-called “faithful,” thereby delineating nonconformists from conformists. Often, these persecutions can be shown to mask ulterior motives, such as appropriating the wealth and property of those so targeted, while also serving as instruments of interethnic strife among different biocultural groups competing for sociopolitical supremacy. Because there have been too many historical Inquisitions to cover in a single chapter, we focus on two specific test cases for these hypotheses: (1) the Medieval Episcopal and Papal Inquisitions against the heterodox Christian sectarians in the south of France; and (2) the Royal Spanish Inquisition of the Early Modern Era against the Conversos or “New Christians” of Spain. We show how an examination of these particulars supports the expectations of Multilevel Selection Theory. In both cases, we delve somewhat into the ideological bases of the perceived threats to orthodoxy to better understand what specific characteristics of the targeted groups triggered the sociological equivalent of a strong immunological reaction on the part of the persecuting regimes.