Pope Benedict XVI (born Joseph Alois Ratzinger; 16 April 1927 – 31 December 2022) was the head of the Catholic Church and sovereign of the Vatican City from 2005 until his resignation in 2013. Following his resignation, he chose to be known as "pope emeritus", a title he held until his death on 31 December 2022. In addition to this, he was an important philosopher and theologian of the 20th and early 21st centuries. Ordained as a priest in 1951 in Bavaria, Ratzinger embarked on an academic career and established himself as a highly regarded theologian by the late 1950s. He was appointed a full professor in 1958 when aged 31. After a long career as a professor of theology at several German universities, he was appointed Archbishop of Munich and Freising and created a cardinal by Pope Paul VI in 1977, an unusual promotion for someone who had only been ordained to the episcopate less than a month prior and not having much pastoral experience. In 1981, he was appointed Prefect of the Congregation for the Doctrine of the Faith, one of the most important dicasteries of the Roman Curia. In 2002, he also became Dean of the College of Cardinals. Before becoming pope, he had been "a major figure on the Vatican stage for a quarter of a century"; he had had an influence "second to none when it came to setting church priorities and directions" as one of John Paul II's closest confidants. Following the death of John Paul II on 2 April 2005, a conclave elected Ratzinger as his successor on 19 April; he chose Benedict XVI as his papal name in honour of Benedict XV and Benedict of Nursia. Benedict's writings were prolific and generally defended traditional Catholic doctrine, values, and liturgy. He was originally a liberal theologian but adopted conservative views after 1968. During his papacy, Benedict advocated a return to fundamental Christian values to counter the increased secularisation of many Western countries. He viewed relativism's denial of objective truth, and the denial of moral truths in particular, as the central problem of the 21st century. Benedict also revived several traditions and permitted greater use of the Tridentine Mass. 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 also established personal ordinariates for former Anglicans and Methodists joining the Catholic Church. Benedict's handling of sexual abuse cases within the Catholic Church and opposition to usage of condoms in areas of high HIV transmission were criticized by public health officials, anti-AIDS activists, and victims' rights organizations. Citing health reasons due to his advanced age, Benedict resigned as pope on 28 February 2013. He became the first pope to resign from office since Gregory XII in 1415, and the first without external pressure since Celestine V in 1294. He subsequently moved into the newly renovated Mater Ecclesiae Monastery in Vatican City for his retirement. The 2013 conclave elected Francis as his successor on 13 March. In addition to his native German language, Benedict had proficiency in French, Italian, English, and Spanish. He also knew Portuguese, Latin, Biblical Hebrew, and Biblical Greek. He was a member of several social science academies, such as the French Académie des Sciences Morales et Politiques.