On this day, 462 years ago, on December 29, 1563 (December 15, 1563 lunar calendar), the theologian Castellio died. Sebastian Castellio (also Chataillon, Castellión or Castello, 1515 - December 29, 1563), French missionary and theologian, and a leading advocate of religious freedom and freedom of conscience in the 16th century. In Christian theology, Castellio is considered an anti-Trinitarian. Born in 1515, Castellio studied at the University of Lyon in France and worked with Calvin in Strasbourg and Geneva until he was removed as dean of the Geneva Academy in 1544 due to differences in religious principles. In 1553, Castellio was appointed professor of Greek at the University of Basel in Switzerland. In 1563, Castellio died of poverty and illness at the age of 48, and was buried in Münster, Germany. His body was later exhumed, and later crushed to ashes. In 1554, Castellio published "Dehaereticis" under the pseudonym "Martinus Bellius". In it, he wrote for Servetus, the Spanish medical scientist and theologian who was burned at the stake by Calvin in Geneva: "When Servetus fights with reason and words, he should only be countered by reason and words." J. Frank Schulman of the Institute for the Advancement of Universalists (or "Unitarian Society") pointed out that Castellio may be "the first person in history who can be called a monotheist in modern terms." Castellio advocated religious tolerance throughout his life, especially refuting the government's expulsion of non-believers. The book "Dehaereticis" (ContralibellumCalvini) "Grief Appeal to France" (ConseilalaFrancedesolee) "On Skepticism" (Deartedubitandi) commented that religions are all about fraternity, and it is logical to allow heresy to exist.