Ultimately he settled down to metaphysical and ethical inquiries, and devoted to these the last thirteen years of his life. During his undergraduate years the two intellectual forces most powerful at Oxford had been the writings of J. H. Newman in the religious sphere, though their influence was already past its meridian, and the writings of John Stuart Mill in the sphere of logic and philosophy. By neither of these, save in the way of antagonism, had Green been influenced. He heartily hated all the Utilitarian school, and had an especial scorn for Buckle, who, now almost forgotten, enjoyed in those days, as being supposed to be a philosophic historian, a brief term of popularity. Green had been led by Carlyle to the Germans, and his philosophic thinking was determined chiefly by Kant and Hegel, more perhaps by the former than by the latter, for it was always upon ethical rather than upon purely metaphysical problems that his mind was bent. His religious vein and his hold upon practical life made him more interested in morals than in abstract speculation. Thus he became the leader in Oxford of a new philosophic school which looked to Kant as its master, and which for a time, partly perhaps because it effectively attacked the school of Mill, received the adhesion of some among the most thoughtful of the younger High Churchmen. Like Kant, he set himself to answer David Hume, and the essay prefixed to his edition of Hume's _Treatise on Human Nature_. along with his _Prolegomena to Ethics_, are the only books in which his doctrines have been given to the world, for he did not live to write the more systematic exposition he had planned. These two essays are hard reading, for his philosophical style was usually technical, and sometimes verged on obscurity. But when he wrote on less abstruse matters he was intelligible as well as weighty, full of thought, and with an occasional underglow of restrained eloquence. The force of character and convictions makes itself felt through the language.