Regarded as the greatest figure of scholasticism, he also devised the official Roman Catholic tenets as declared by Pope Leo XIII. His works include many commentaries on Aristotle as well as the Summa Contra Gentiles (intended as a manual for those disputing with Spanish Muslims and Jews). His principal achievement was to make the work of Aristotle acceptable in Christian western Europe; his own metaphysics, his account of the human mind, and his moral philosophy were a development of Aristotle’s, and in his famous arguments for the existence of God (‘the Five Ways’) he was indebted to Aristotle and to Arabic philosophers.