Popes have never been enthusiastic about Freemasonry. Clement XII condemned the order in 1738, as did Benedict XIV in 1751. This was followed by interdicts by Pius VII in 1821, Leo XII in 1826, Pius VIII in 1829, Gregory XVI in 1832, and Pius IX 1646. The encyclical Humanum Genus by Leo XIII was the most ambitious attack yet, and linked Masonry to deism and Gnosticism. It remains perhaps the most sweeping condemnation by the Roman Catholic Church of the Masonic movement, and has been the source of considerable conflict and confrontation ever since it was issued.