His prolific writings generally defend traditional Catholic doctrine and values. He was originally a liberal theologian, but adopted conservative views after 1968. During his papacy, Benedict XVI advocated a return to fundamental Christian values to counter the increased secularisation of many Western countries. He views relativism's denial of objective truth, and the denial of moral truths in particular, as the central problem of the 21st century. He taught the importance of both the Catholic Church and an understanding of God's redemptive love. Benedict also revived a number of traditions, including elevating the Tridentine Mass to a more prominent position. He strengthened the relationship between the Catholic Church and art, promoted the use of Latin, and reintroduced traditional papal vestments, for which reason he was called "the pope of aesthetics". He has been described as "the main intellectual force in the Church" since the mid-1980s.