Gratian, fl. 1140, Italian legal scholar, founder of the science of canon law. Almost nothing is known of his life beyond the fact that he was a monk, almost certainly Camaldolite, and that he taught at the convent of saints Felix and Nabor (San Felice) in Bologna. He was apparently very learned in scholasticism and Roman law. His great work, commonly known as the Decretum, appeared c.1140. It is a synthesis of church law, divided into three parts: the first deals with sources and principles of canon law and with ecclesiastical persons; the second, with ecclesiastical jurisdiction and property and to some extent with marriage and penance; the third, with sacraments and liturgy. Gratian, by his method, makes the compilation a systematic treatise; his commentaries, the dicta Gratiani, make up a large part of the work. The Decretum was used by the later popes and became the kernel of the Corpus juris canonici.