Epicurus - Letter to Herodotus 45 (Bailey)
These brief sayings, if all these points are borne in mind, afford a sufficient outline for our understanding of the nature of existing things. Furthermore, there are infinite worlds both like and unlike this world of ours. For the atoms being infinite in number, as was proved already, are borne on far out into space. For those atoms, which are of such nature that a world could be created out of them or made by them, have not been used up either on one world or on a limited number of worlds, nor again on all the worlds which are alike, or on those which are different from these. So that there nowhere exists an obstacle to the infinite number of the worlds.
Lucretius Book 2-1023 (Life On Other Worlds; Nature Never Makes A Single Thing of A Kind)
Now turn your mind, I pray, to a true reasoning. For a truth wondrously new is struggling to fall upon your ears, and a new face of things to reveal itself. Yet neither is anything so easy, but that at first it is more difficult to believe, and likewise nothing is so great or so marvelous but that little by little all decrease their wonder at it. First of all the bright clear color of the sky, and all it holds within it, the stars that wander here and there, and the moon and the sheen of the sun with its brilliant light; all these, if now they had come to being for the first time for mortals, if all unforeseen they were in a moment placed before their eyes, what story could be told more marvelous than these things, or what that the nations would less dare to believe beforehand? Nothing, I trow: so worthy of wonder would this sight have been. Yet think how no one now, wearied with satiety of seeing, deigns to gaze up at the shining quarters of the sky! Wherefore cease to spew out reason from your mind, struck with terror at mere newness, but rather with eager judgement weigh things, and, if you see them true, lift your hands and yield, or, if it is false, gird yourself to battle.
For our mind now seeks to reason, since the sum of space is boundless out beyond the walls of this world, what there is far out there, whither the spirit desires always to look forward, and whither the unfettered projection of our mind flies on unchecked.
2-1048
First of all, we find that in every direction everywhere, and on either side, above and below, through all the universe, there is no limit, as I have shown, and indeed the truth cries out for itself and the nature of the deep shines clear. Now in no way must we think it likely, since towards every side is infinite empty space, and seeds in unnumbered numbers in the deep universe fly about in many ways driven on in everlasting motion, that this one world and sky was brought to birth, but that beyond it all those bodies of matter do naught; above all, since this world was so made by nature, as the seeds of things themselves of their own accord, jostling from time to time, were driven together in many ways, rashly, idly, and in vain, and at last those united, which, suddenly cast together, might become ever and anon the beginnings of great things, of earth and sea and sky, and the race of living things. Wherefore, again and again, you must needs confess that there are here and there other gatherings of matter, such as is this, which the ether holds in its greedy grip.
2-1067
Moreover, when there is much matter ready to hand, when space is there, and no thing, no cause delays, things must, we may be sure, be carried on and completed. As it is, if there is so great a store of seeds as the whole life of living things could not number, and if the same force and nature abides which could throw together the seeds of things, each into their place in like manner as they are thrown together here, it must needs be that you confess that there are other worlds in other regions, and diverse races of men and tribes of wild beasts.
2-1077
This there is too that in the universe there is nothing single, nothing born unique and growing unique and alone, but it is always of some tribe, and there are many things in the same race. First of all turn your mind to living creatures; you will find that in this wise is begotten the race of wild beasts that haunts the mountains, in this wise the stock of men, in this wise again the dumb herds of scaly fishes, and all the bodies of flying fowls. Wherefore you must confess in the same way that sky and earth and sun, moon, sea, and all else that exists, are not unique, but rather of number numberless; inasmuch as the deep-fixed boundary-stone of life awaits these as surely, and they are just as much of a body that has birth, as every race which is here on earth, abounding in things after its kind.
Isonomia
Cicero - On The Nature of The Gods - Book 1 (Yonge)
XIX. These discoveries of Epicurus are so acute in themselves and so subtly expressed that not everyone would be capable of appreciating them. Still I may rely on your intelligence, and make my exposition briefer than the subject demands. Epicurus then, as he not merely discerns abstruse and recondite things with his mind's eye, but handles them as tangible realities, teaches that the substance and nature of the gods is such that, in the first place, it is perceived not by the senses but by the mind, and not materially or individually, like the solid objects which Epicurus in virtue of their substantiality entitles steremnia; but by our perceiving images owing to their similarity and succession, because an endless train of precisely similar images arises from the innumerable atoms and streams towards the gods, our mind with the keenest feelings of pleasure fixes its gaze on these images, and so attains an understanding of the nature of a being both blessed and eternal.
Moreover there is the supremely potent principle of infinity, which claims the closest and most careful study; we must understand that it has the following property, that in the sum of things everything has its exact match and counterpart. This property is termed by Epicurus isonomia, or the principle of uniform distribution. From this principle it follows that if the whole number of mortals be so many, there must exist no less a number of immortals, and if the causes of destruction are beyond count, the causes of conservation also are bound to be infinite.
You Stoics are also fond of asking us, Balbus, what is the mode of life of the gods and how they pass their days. The answer is, their life is the happiest conceivable, and the one most bountifully furnished with all good things. God is entirely inactive and free from all ties of occupation; he toils not neither does he labor, but he takes delight in his own wisdom and virtue, and knows with absolute certainty that he will always enjoy pleasures at once consummate and and everlasting.