Extraterrestrial Life Debate, Antiquity to 1915: A Source Book

1. THE DEBATE IN ANTIQUITY

THE DEBATE IN ANTIQUITY THE ATOMISTS When in Western thought did the debate over the existence of extraterrestrial intelligent life commence? Classical scholars date that development from Greek antiquity , in particular, from the fifth century BCE, when Leucippus and Democritus advocated the existence of such beings.1 Although only fragments from their writings have been preserved, ample testimony from antiquity indicates that they advocated the existence of other worlds. For example, Hippolytus, a third century CE theologian, recorded that Democritus holds the same view as Leucippus about the elements, full and void . . . he spoke as if the things that are were in constant motion in the void; and there are innumerable worlds, which differ in size. In some worlds there is no sun and moon, in others they are larger than in our world, and in others more numerous. (3) The intervals between the worlds are unequal; in some 1. G. S. Kirk and J. E. Raven, The Presocratic Philosophers (Cambridge: Cambridge University Press, 1964), 121–26 and 409–14. O O N N E E 3 a n t i q u i t y t o n e w t o n 4 2. As translated in Kirk and Raven, Presocratic Philosophers, 411. 3. Epicurus, “Epicurus to Herodotus,” trans. C. Bailey, in The Stoic and Epicurean Philosophers, ed. Whitney J. Oates (New York: Modern Library, 1957), 5. parts there are more worlds, in others fewer; some are increasing, some at their height, some decreasing; in some parts they are arising, in other failing. They are destroyed by collision one with another. There are some worlds devoid of living creatures or plants or any moisture.2 Leucippus and Democritus were atomists, that is, they believed that matter is ultimately composed of tiny particles in constant motion. In fact, their belief in “innumerable worlds” derived from their atomistic doctrine. Given the random motions of an infinite number of atoms, chance would produce the formation of other worlds. In understanding this passage it is important to recognize that by the term world they (as well as essentially all other ancient authors) did not mean another solar system comparable to our own and at least in principle visible to us. Rather they were referring to a cosmos comparable to our own with an earth at the center and with planets and a stellar vault surrounding it. The atomist (or as it is sometimes called, the materialist) tradition in philosophy remained alive for many centuries in the ancient world. Two prominent later atomists were Epicurus and Lucretius, both of whom also supported the doctrine of innumerable inhabited worlds. Epicurus, who died around 270 BCE, championed the doctrine of a plurality of worlds in a number of his writings, for example, in a letter he wrote to his disciple Herodotus. Early in that letter, Epicurus presents his atomic theory. Soon thereafter , he expresses his views on other worlds: Furthermore, there are infinite worlds both like and unlike this world of ours. For the atoms being infinite in number . . . are borne 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 worlds.3 That extraterrestrial beings inhabit these worlds is clear from a passage later in the letter: Furthermore, we must believe that in all worlds there are living creatures and plants and other things we see in this world; for indeed no one could prove that in a world of one kind there might or might not have been included the kinds of seeds from which living things and plants and all the rest of the things we see are composed, and that in a world of another kind they could not have been.4 Given Epicurus’s claims that atoms and the void are the sole constituents of the universe, that all things come to be through the chance collision of these atoms, and that (and thereby) a plurality of worlds is formed, it is not surprising that Epicurus goes on to reject traditional theological views. Such views had been used to explain many phenomena that Epicurus...