23 And above all, when the integrity of Catholic faith and morals - the sacred heritage handed down by our forefathers - was jeopardized, especially by the activities of Abelard, Arnold of Brescia and Gilbert de la Poree, strong in the grace of God he spared no pains in writing works full of penetrating wisdom and making tiring journeys, so that errors might be dispelled and condemned, and the victims of error might as far as possible be recalled to the straight path and to virtuous living.
Source: Doctor Mellifluus (Vatican.va)