THE MEDIEVAL REVIVAL OF LEARNING 379 world was made by God and discusses the Trinity at some length; next he considers other spiritual beings in the uni- verse, such as the demons in whom medieval men generally believed ; and then he treats of the elements of which natu- ral objects are composed. Here he makes use of the writings of Constantinus Africanus, who, while still accepting the old Greek theory of only four elements, had explained that the earth, air, fire, and water which we see and feel are not the pure elements, but, like all other objects in nature, are compounds made up of all four elements. Finally, William discusses in more detail the sky and stars, and the earth and its human occupants. Other interests of the learned world of the twelfth cen- tury are illustrated by the career of Abelard (1079-1142), the oldest son of the lord of a village in Brittany, who left castle, the chase, and the profession of arms, to pursue learning. He was especially interested in dialectic or logic, the art of reasoning and disputation. This was a subject not unlike the debating of our day except that the questions argued were philosophical and theological rather than political and economic as in intercollegiate de- bates of the present — questions about the workings of the mind rather than about money matters, and questions con- cerning the other world rather than this. Abelard found many places where teachers were instructing large bands of students in the art of logic, and he himself before long be- came a lecturer of great renown at Paris. Dialectic was based upon the treatises of Aristotle in logic which had been translated by Boethius and Porphyry at the close of the Roman Empire. Teachers and stu- Medieval dents of dialectic were now exercised over such nominalists questions as whether there is any such reality as and realists color independent of the colored objects. In other words, whether we merely have red paint and red cows and red sunrises, or whether there is a redness apart from particular objects. Or, furthermore, whether there is an ideal beauty and an abstract justice which form our standards in deter- mining whether individual objects are beautiful and whether
