Known as the "prince of physicians," Avicenna made enormous contributions to the fields of medicine, natural history, metaphysics, and religion. His use of Aristotelian logic and his work on the concept of "being" opened the door for a rationalist study of religion, influencing the later Christian philosophers Aquinas, Descartes, and Kant. Avicenna's monumental Canon of Medicine is regarded as possibly the greatest medical work ever. Available in a Latin translation in Europe one hundred years after his death, it continued to be used there for the next six centuries.