Final answer:
Ad abolendam was a papal bull issued by Pope Lucius III in 1184, significant for establishing procedures to combat heresy and aiding in the foundation of the medieval Inquisition.
Step-by-step explanation:
Ad abolendam is a papal bull that was issued by Pope Lucius III in the year 1184. It is significant for being one of the foundational documents in the establishment of the medieval Inquisition. Its primary purpose was to abolish heresy within Christendom, giving bishops the authority to identify and take action against heretics.
The document was further endorsed and developed by subsequent popes, including Pope Innocent III, but it was initially established through the authority of Pope Lucius III. The bull laid the groundwork for legal procedures against heresy, marking a pivotal moment in the history of the Catholic Church's approach to heresy and nonconformity within its ranks.