Known as the "e;prince of physicians,"e; 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 "e;being"e; 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.