Ibn Sina - Avicenna in Latin - (980-1037) played a considerable role in the development of both eastern and western philosophy and science. His contributions to the fields of logic, natural science, psychology, metaphysics and theology and even medicine are difficult to overstate. The great Islamic philosopher al-Ghazali thought that if one could show the incoherence of Avicenna's thought, then one would have shown the incoherence of philosophy in general. No other author is directly cited by Thomas Aquinas more often than Avicenna. But Avicenna's significance and influence do not stop with the medieval period. His logic, natural philosophy, and metaphysics are still taught in the Islamic world as living philosophy. And many contemporary Catholic and evangelical Christian philosophers still come under his influence through Aquinas's work.