I happen to be reading through various Medieval texts on the question of the eternity of the world, so I’ll deposit a few thoughts here as I go along. I will be revisiting Bonaventure and Aquinas on this issue in the coming weeks but for now my focus is on selections from King’s translation of Siger’s De aeternitate mundi.
Siger of Brabant’s reading of Aristotle presents a helpful contrast to Bonaventure’s view (which I will present sometime soon) because they both represent the various poles – one sided furiously loyal to Aristotle and the other to Plato.
Siger accepts Aristotle’s arguments from Physics 8 and De Generatione et Corruptione, namely, that the Universe is eternal, yet not “eternal” in the same way as the First Mover. The existence of the First Mover curbs the logical paradox of an infinite regress, thus placing a limit on finitude by means of the division between potency and act. However, the Universe is eternal in the same way that circular motion is eternal. Any “beginning” in circular motion must be preceded by another “beginning” and another and so on. Thus, individual species are also eternal. Any concept of a “first” man presupposes temporality and there could not have been a time before time when “man” would have not existed since time is the measure of motion and motion is circular.
From [§ 22] it follows that the human species, according to philosophers, always exists, and that it did not begin to exist at a time when it had not previously existed at all. For to say that [the species] will have begun to exist at a time when it had not previously existed at all is to say that some individual belonging to the [species] will have begun to exist, before which there existed no other individual belonging to that species. And since the human species is not caused in any other way, according to philosophers, save as having been generated through the generation of [one] individual before [another] individual, the [species] began to exist. Even though in every case everything generated begins to exist, still, [the species] begins to exist, since it did exist and previously had existed. (De aeternitate mundi, I.24.)
This is all quite perplexing partly because “eternity” strains the capacities of reason.
Now, what if we add a further complication to this in order to understand what the implications of this doctrine of the eternity of the world would have on the doctrine of God or the Prime Mover? It seems that for Siger – and as it appears for Aristotle also – the Prime Mover, defined as “thought thinking on thinking” (nous noêsis noeseôs) does not comprehend the totality of existing things within itself without those things simultaneously (if that word works) existing as individuals sempiternally. In other words the Prime Mover does not create based on “forms” that preexist as perfections of the things existing in reality but rather knows itself in the manner of a species within the existing individual species. The division between Prime Mover and “species” is purely logical just as the division between thought, thinking, and thing thought is purely logical. I’d be happy to entertain correction to my reading of Siger but, as it stands, it seems to me that his interpretation of Aristotle represents a more nominalist epistemology than realist of any variety.