PROOEMIUM.

astronomers. And therefore, at that time, we will be the same in number, and we will sit in this or that school or lecture hall, just as we do now, namely, in the great year. Hence Plato said that after the great year he must return to Athens, and he must lecture there. The reason is that the entire constellation will return in the same way. Therefore, with the return of the same constellation, the same affections will return. It has been said, according to the opinion of Averroes and Aristotle in the fifth book of the Physics and in the book On Generation, that it is not possible for those generations not to exist then immediately, and the corruptions, therefore, time would mediate. And thus, one in number is lost by one mutation, according to the fifth book of the Physics. But regarding the first doubt, it must be said that after the great year, it is possible for men to return who are very similar, such that they can scarcely be distinguished, although they are not the same in number. But you might say, if the cause and matter remain the same, the effect will be the same in number. The answer is that this is true if the same measure and matter are equally disposed, but this is not the case because time passes rapidly and does not return the same in number, although it does return the same in species. And it may be said that today's resolution is not the same in number as the resolution that comes after a thousand or four hundred years, because motion is a successive entity. The second doubt is whether one animal can be perpetuated forever. And it seems that it can, because it is possible to find something complex in which the elements are reduced to a mean or a middle proportion,