Scotism is the philosophical school and theological system named after John Duns Scotus, a 13th-century Scottish philosopher-theologian. The word comes from the name of its originator, whose Opus Oxoniense was one of the most important documents in medieval philosophy and Roman Catholic theology, defining what would later be declared the dogma of the Immaculate Conception by Pope Pius IX in his constitution Ineffabilis Deus on 8 December 1854.