Bernard of Clairvaux, O.Cist (1090 – August 20, 1153) was a Frankish abbot and the primary builder of the reforming Cistercian monastic order. After the death of his mother, Bernard sought admission into the Cistercian order. Three years later, he was sent to found a new abbey at an isolated clearing in a glen known as the Val d'Absinthe, about 15 km southeast of Bar-sur-Aube. According to tradition, Bernard founded the monastery on 25 June 1115, naming it Claire Vallée, which evolved into Clairvaux. There Bernard would preach an immediate faith, in which the intercessor was the Virgin Mary. In the year 1128, Bernard assisted at the Council of Troyes, at which he traced the outlines of the Rule of the Knights Templar, who soon became the ideal of Christian nobility.
On the death of Pope Honorius II, which occurred on February 14, 1130, a schism broke out in the Church. King Louis VI convened a national council of the French bishops at Étampes, and Bernard was chosen to judge between the rival popes. In 1139, Bernard assisted at the Second Council of the Lateran. Bernard denounced the teachings of Peter Abelard to the Pope, who called a council at Sens in 1141 to settle the matter. Bernard soon saw one of his disciples, Bernard of Pisa, elected Pope. Having previously helped end the schism within the Church, Bernard was now called upon to combat heresy. In June 1145, Bernard traveled in Southern France and his preaching there helped strengthen support against heresy.
Following the Christian defeat at the Siege of Edessa, the Pope commissioned Bernard to preach the Second Crusade. The last years of Bernard's life were saddened by the failure of the crusaders, the entire responsibility for which was thrown upon him. Bernard died at age 63, after 40 years spent in the cloister. He was the first Cistercian monk placed on the calendar of saints, and was canonized by Pope Alexander III on 18 January 1174. Pope Pius VIII bestowed upon him the title of "Doctor of the Church."