 It was about 1150 that Gratian, professor of theology at the University of Bologna and sometimes believed to have been a Camaldolese monk, composed the work entitled by himself "Concordia discordantium canonum", but called by others "Nova collectio", "Decreta", "Corpus juris canonici", also "Decretum Gratiani", the latter being now the commonly accepted name.He did this to obviate the difficulties which beset the study of practical, external theology ("theologia practica externa"), i. e. the study of canon law.In spite of its great reputation and wide diffusion, the "Decretum" has never been recognized by the Church as an official collection.