In 1024 Gerard called a synod in Arras to confront a purported heresy fomented by the Gundulfian heretics, who denied the efficacy of the Eucharist.
The records of this synod, the Acta Synodi Atrebatensis,[3] preserve a summary of orthodox Christian doctrine of the early eleventh century, as well contemporary peace-making practices.
[citation needed] He was a student of the great Gerbert of Aurillac, the leading theologian of the tenth century, and a supporter of the monastic reformer Richard of Verdun, abbot of Saint-Vanne.
[8] Writing between 1023 and 1025, he observed, in the words of Georges Duby, "that there were distinctions between men, an essential inequality which could be compensated only by charity, mercy and mutual service" within the framework of divinely ordained natural law.
[9] In addition to his role in the Investiture Controversy, Gerard was a voice in the implementation of the Peace and Truce of God movement to limit warfare.