SECTION 13. -- The beginning of this World.

Thesis XXI. -- The universe, considered in its chief processes, had a beginning.

105. Having stated our opinion about the possibility of eternal creation in the abstract, another question remains to be answered. Can the particular world in which we live have existed from eternity?

The meaning of this question is not whether the innumerable species of creatures which constitute the world known to man can have been created without a beginning. Even the conclusions of natural science indicate that all living beings which people the earth, if considered not in the germ of their species, but in their specific nature itself, had their origin long after the creation of matter. We intend only to ask: Was it intrinsically possible, and consequently in the power of the Almighty, to decree that the chief processes of nature should go on without ever having had any beginning? This question may be resolved into the following three:

1. Can there have been motion of matter without a beginning of motion?

2. Is evolution of vegetable and animal life possible without a beginning of evolution?

3. Can the generations of mankind have succeeded one another for all ages without there being any first parents or first children?

To each of these questions we answer in the negative.

106. And first as regards motion of matter. Motion is not an instantaneous act, but involves really different successive phases. There is no motion of matter without continuous changes of position of material particles. The concept of motion and the concept of succession are inseparable from one another. But succession cannot have existed from eternity. In it a "sooner" and a "later" are necessarily involved. Every "later" had evidently a beginning, and consequently every "sooner," which is essentially related to a "later" -- in other words, every "sooner" which constitutes a part of succession must have had a beginning. Bearing now in mind that succession is involved in motion so as to be necessarily connected with the movements of material particles, we must pronounce it metaphysically impossible that motion of matter should have been without a first start or beginning of motion.

This conclusion opens the way to the other, that evolution of life, the processes of assimilation and decomposition, of generation and corruption in animate matter, are inconceivable unless they have had a beginning. They all imply succession, and consequently can have had but a limited duration.

107. Coming now to the human race, it must have had a beginning not only for the reasons just given, but also because the number of human souls that possibly can exist can never be actually infinite. Such a number is intrinsically impossible, as we have shown in our chapter on infinity. (§ 66.) But if mankind had existed from eternity, the number of human souls that existed at any given moment, if we suppose that none of these naturally incorruptible beings is annihilated by the absolute power of God, would really be actually infinite. Whatever therefore may be our opinion on the absolute possibility of an eternal creature, there can be no doubt that a universe like ours, in which there is motion and organic life, and in which one generation of men follows another, cannot have existed from eternity, considered even in its most fundamental features.^{32}

We have treated here the question of the duration of our world only from a metaphysical point of view. So far as the existence in the past of the present state of our solar system, of organic life and of man is concerned, the theories of modern astronomers, of geologists and paleontologists support our conclusions.

On the other hand, Aristotle opposes them inasmuch as they rest upon the impossibility of motion without a beginning. The arguments by which he endeavoured to prove that motion must be without a beginning, together with modern arguments in favour of eternal creation, will find their solution in the following chapter.

{32} Our thesis is supported by Cardinal Zigliara, who arrives at the same conclusions in a way somewhat different. His words are: "Existimo autem mundum uti nunc est, non potuisse ab aeterno creari. . . . Etenim ci creatio ista foret possibilis, consequi videtur quod in successione ab aeterno usque ad praesens forent, in facta hypothesi, actu infinitae successiones vel in tempore, vel in moto, vel in generatione, vel saltem in cogitationibus alicujus mentis creatae." (Summa Philosophica, Vol. II. pp. 38, 39.)