This dual-language book is a translation of John Pecham's De aeternitate mundi (On the Eternity of the World), written probably in 1270. Pecham was born in England around 1230. He pursued studies in Paris, where he may have been a student of Roger Bacon's, and at Oxford. He returned to Paris some time between 1257 and 1259 to study theology and in 1269-1270 became magister theologiae. It was at this time that he presumably wrote the essay translated here, and presented it as part of his inception, the equivalent of a doctrinal defense, in 1271, when he sought to become a magister regens, a member of the theological faculty. While Pecham was studying in Paris, two controversial theological innovationswere being debated. The first issue involved the founding of the mendicant orders (Franciscans and Dominicans) in the first decade of the thirteenth century. Their active moving about, preaching and teaching, represented a departure from the established Rule of St. Benedict in which Orders were largely confined to monasteries. The second debate was over the introduction of the newphilosophy of Aristotle. The Dominicans and Franciscans found themselves allied against the Latin Averroists (or Radical Aristotelians) on such issues as the unicity of the intellect and the assertion of the world's eternity in the sense that is was not created. The two Orders disagreed, however, on the truth of other Aristotelian theses such as the unicity of substantial form and the demonstrability of the world's having a beginning in time. On another front, having to do with the legitimacy of the Dominicans and Franciscans interpretation of religious life, the two Orders united under attacks from the secular clergy. Pecham, a Franciscan, witnessed his Order allied with the Dominicans against Averroists and secular clergy, and at odds with them over Aristotelianism in orthodox theology. During this tumultuous time Pecham met, and probably discussed his inception with Thomas, and his position on the eternity of the world can be compared to the treatment of the topic found in the writings of St. Thomas Aquinas and St. Bonaventure. In 1279, Pecham was named the Archbishop of Canterbury by Pope Nicolas III, in this position it was expected that he carry out reforms mandated by the Council of Lyons. The ruling of that council included the eradication of the Averroists radical departures from theological philosophy and some of the theses held by the Thomists. Pecham died in 1291, no doubt in disappointment that the reforms for which he had strived never came to pass.