May 15: edit
- 1252 - Pope Innocent IV issues the papal bull ad exstirpanda, which authorizes the torture of heretics in the Medieval Inquisition. Torture quickly gains widespread usage across Catholic Europe.
- 1961 - The Unitarian Universalist Association was created via consolidation of the American Unitarian Association and the Universalist Church of America. This consolidation brought into existence the liberal religion known as Unitarian Universalism.