In opposition to the teaching of St Thomas Aquinas he argued that faith was a matter of will, not dependent on logical proofs. He was also the first major theologian to defend the theory of the Immaculate Conception. His system was accepted by the Franciscans as their doctrinal basis and exercised a profound influence in the Middle Ages. In the Renaissance his followers were ridiculed for their conservatism and abused as enemies of learning, which gave rise to the word dunce.