#OTD in 1140. The French scholar Peter Abelard is found guilty of heresy at the Council of Soissons.
This council was convened by the Church to examine his book "Theologia Summi Boni", which was seen as challenging orthodox Christian doctrine. Abelard's rational approach to theology and his emphasis on applying logic to faith led to suspicions among church authorities.
Books by Peter Abelard at PG:
https://www.gutenberg.org/ebooks/author/5441