The problem of the eternity of the world was much debated in Western philosophy from the twelfth through the fourteenth centuries, but its history goes back as far as Philo of Alexandria and the Church Fathers. The principal topic of controversy was the possibility of a beginningless and yet created world. The arguments that fashioned the medieval discussion rested upon assumptions concerning the concepts of eternity and creation. In addition, the issue of eternity intertwined with discussions of the relationship of God to creation, with proofs of the existence of God, with the nature of the material universe and with the nature of infinity. Some of the most ingenious ideas in these debates were obtained from pagan Greek, Islamic and Jewish traditions.
According to Judaeo-Christian tradition, based in particular upon the opening words of Genesis ('In the beginning God created the heaven and the earth'), the universe had a beginning. From the fourth century onwards, however, Christian thinkers had to take into consideration accounts from antiquity, transmitted by authors such as Augustine and Boethius, according to which the existence of the material universe (mundus) was 'from eternity' (ab aeterno), that is, beginningless.
In its early stages, the medieval discussion of the eternity of the world was preoccupied with two types of questions, one asking whether the world had existed from eternity and the other examining the concept of eternity and its relation with time. In general, 'time' (tempus) was understood to imply having both a beginning and an end, and perpetuity (aevum) involved a beginning but not an end, whereas 'eternity' (aeternitas) had neither beginning nor end. 'Eternity' in this sense was understood as a temporal notion, meaning 'infinite temporal extension'. However as Boethius pointed out in De consolatione philosophiae (The Consolation of Philosophy), 'eternity' could also be taken as atemporal. This conception of eternity, sometimes called 'eternity proper' by later authors, introduced the notion of timelessness within the notions of 'all at once' (tota simul) and of 'life', and referred to God's mode of existence.
Medieval thinkers all agreed that the universe was not coeternal with God. They were divided, however, over the question whether the universe had always existed in a temporal sense, and over how this question should be understood in the first place. Using a distinction derived from Augustine in De civitate Dei (The City of God) and Confessiones (Confessions), many medieval thinkers would observe that the world was created together with time, and in this sense had always existed: there was no past at the time of creation.
In the early thirteenth century, the discussion of the eternity of the world was raised to a higher level. Three events contributed to this. First, the Fourth Lateran Council (1215) declared the temporal beginning of the world to be an article of faith. Second, around that same time the Sentences by Peter Lombard, which included a statement (Book 2, distinction 1) about the world's eternity, became an official textbook in the faculty of theology. Third, the translation into Latin of Aristotle's books on natural philosophy (Libri naturales), especially Physics VIII, brought medieval thinkers in the arts faculty into routine contact with arguments proving the eternity of motion and generation (see Aristotle). Aristotle's views on eternity, especially the question whether he had intended to prove the beginninglesness of the world, became an issue of debate that culminated in the condemnations of 1270 and 1277 by Bishop Etienne Tempier (see Aristotelianism, medieval). Aristotle's views were perceived through the interpretations offered by Averroes' Commentary on Aristotle's Physics and Maimonides' Guide to the Perplexed, works that had also been translated recently into Latin (see Averroism; Ibn Rushd; Maimonides, M.).
The most important result of these events was that the issue to be debated came into sharper focus: could the world have been eternal, if God had so willed? In other words, must the beginning of the world be accepted as an article of faith, or can it also be proved by (demonstrative) arguments? In this way, the issue of the eternity of the world helped to determine the position philosophers held with regard to the relation between faith and reason.
The various conceivable ways of responding to the question of the eternity of the world can be reduced to the following two positions. One group of thinkers, of whom Bonaventure is the archetype, claimed that it could be demonstrated that the world began to exist. Other adherents of this position were Matthew of Aquasparta, Henry of Ghent, John Pecham, Richard of Middleton, Peter Aureol, William of Alnwick, Henry Totting of Oyta and Marsilius of Inghen. The demonstrations hinged on two basic assumptions concerning creation and eternity.
The Christian view had come to be that God had created the world where before there had been nothing: in other words, creation from nothing. In an argument that goes back to Richard of St Victor, it was maintained that since creation from nothing (ex nihilo) is a transition from non-being (nihil) to being, non-being necessarily precedes being. Hence, creation necessarily implies a beginning in time. In sum, creation 'from nothing' was understood as creation 'after nothing' (post nihil).
Furthermore, an eternal world was conceived to imply the existence of an infinite series of past events. The contradictions that allegedly arose from this assumption were considered reasons why an eternal world is impossible. Most of the arguments were drawn from Aristotle's widely accepted theory of the infinite, but were here employed in a new context to substantiate the un-Aristotelian conclusion that the world is not eternal but had a beginning. In particular, the following generally accepted Aristotelian rules were considered to be violated by the idea of a beginningless world: first, that it is impossible to add to the infinite; second, that it is impossible to traverse what is infinite; third, that it is impossible for the infinite to be grasped by a finite power; and fourth, that it is impossible that there be simultaneously an infinite number of things. In addition, the theory of a possible eternal world seemed to clash with self-evident principles such as that the whole is greater than the part (John Pecham) or that, since the infinite is infinite, one infinity cannot be greater than another, or that there is no order in the infinite because there is no first element (Bonaventure). Some of these alleged contradictions had already been pointed out by John Philoponus in his De aeternitate mundi contra Proclum (On the Eternity of the World Against Proclus) and had circulated among Arabic authors such as Algazel in his Metaphysica before they were transmitted to the Latin West (see al-Ghazali; Islamic philosophy: transmission into Western Europe).
Another group of thinkers, including Siger of Brabant, Boethius of Dacia, Thomas Aquinas, Giles of Rome, Godfrey of Fontaines, William of Ockham, Henry of Harclay, Thomas of Wylton and Thomas of Strasbourg, argued that the universe could have existed from eternity. In part, their argumentation rested on the rebuttal of those arguments that the proponents of a demonstrable beginning had invoked to refute the possibility of an eternal world. They concluded that since the beginning of the world could not be demonstratively proved, the universe could have existed without beginning to exist.
Proponents of the possibility of a beginningless universe interpreted creation out of nothing as creation not out of anything, that is, not out of any independently existing matter. Creation was understood as a relation of causal dependence of creatures upon God, and in this interpretation the status of being a creature was not necessarily inconsistent with being beginningless. The argument that the universe depends for its existence upon a superior principle that is not prior in time but prior in the order of things can be found in Avicenna's Metaphysica, and was at the heart of Aquinas' rebuttal of Bonaventure's interpretation of creation from nothing (see Aquinas, T. §9; Ibn Sina §4).
The infinity arguments in favour of a beginning were considered off the mark by the proponents of the possibility of an eternal world. With regard to the traversal argument, for instance (that is, the argument that if the world had always been, an infinite past time would have been traversed), they emphasized that the traversed infinite time was a successive and not a simultaneous infinity, and hence, that the contradictions that seemed to follow from the premise of an eternal world were not pertinent. There will always be only finitely many past days between this and any past day. A beginningless world does not imply that any past day was infinitely remote from this day.
In general, the adherents of a possible beginningless world held the same Aristotelian views on the infinite as their opponents. They disagreed only over the kind of infinity that was involved in a possible eternal world. Henry of Harclay was an interesting exception. He agreed with his opponents that a possible eternal world would entail an actual infinity, but he denied that the conclusions that followed from this stance were contradictory. Harclay argued that the infinite can be traversed, that it can be exceeded, and that not all infinites are equal (see Infinity).
See also: Aristotelianism, medieval; Creation and conservation, religious doctrine of; Eternity; Natural philosophy, medieval; Richard Rufus of Cornwall; TimeJ.M.M.H. THIJSSEN