14. That vegetables and animals, being once placed upon the earth, have multiplied or are multiplying, so as to occupy every part of the land and water which is suited for their habitation, we can see much reason to believe. Philosophical natural-historians have been generally led to the conviction that each species has had an original centre of dispersion, where it was first native, and that from this centre it has been diffused in all directions, as far as the circumstances of climate and soil were favorable to its production. But we can see also much reason to believe that this general diffusion of vegetable and animal life from centres, is a part of the order of nature which may often be made to give way to other and higher purposes;—to the diffusion, over the whole surface of the earth, of a race of intelligent, moral agents. This process may often interfere with the general law of diffusion: as for instance, when man exterminates noxious animals. And whatever may be the laws which tend to replenish the earth, on which such centres of the diffusion of life exist for animals and plants; according to all analogy, these laws can have no force on any other planet, till such origins and centres of life are established on their surfaces. And even if any of the species which have ever tenanted the earth were so established on any other planet, we have the strongest reason to believe that they could not survive to a second generation.
15. Perhaps it may be said that we unjustifiably limit the power and skill of the Supreme Creator, if we deny that he could frame creatures fitted to live on any of the other planets, as well as in the Earth:—that the wonderful variety, and unexpected resource, of the ways in which animals are adapted for all kinds of climates, habitations, and conditions, upon the earth, may give us confidence that, under conditions still more extended, in habitations still further removed, in climates going beyond the terrestrial extremes, still the same wisdom and skill may well be supposed to have devised possible modes of animal life.
16. To this we reply, that we are so far from saying that the Creator could not place inhabitants in the other planets, that we have attempted to show what kind of inhabitants would be most likely to be placed there, by considering the way in which animals are accommodated to special conditions in their habitation. In judging of such modes of accommodating animals to an abode on other planets, as well as the earth, we have reasoned from what we know, of the mode in which animals are accommodated to their different habitations on the earth. We believe this to be the only safe and philosophical way of treating the question. If we are to reason at all about the possibility of animal life, we must suppose that heat and light, gravity and buoyancy, materials and affinities, air and moisture, produce the same effect, require the same adaptations, in Jupiter or in Venus, as they do on the Earth. If we do not suppose this, we run into the error which so long prevented many from accepting the Newtonian system:—the error of thinking that matter in the heavens is governed by quite different laws from matter on the earth. We must adopt that belief, if we hold that animals may live under relations of heat and moisture, materials and affinities, in Jupiter or Venus, under which they could not live on our planet. And that belief, as we have said, appears to us contrary to all the teaching which the history of science offers us.
17. And not only is it contrary to the teaching of the history of science, to suppose the laws, which connect elemental and organic nature, to be different in the other planets from what they are on ours; but moreover the supposition would not at all answer the purpose, of making it probable that the planets are inhabited. For if we begin to imagine new and unknown laws of nature for those abodes, what is there to limit or determine our assumptions in any degree? What extravagant mixtures of the attributes and properties of mind and matter may we not then accept as probable truths? We know how difficult the poets have found it to describe, with any degree of consistency, the actions and events of a world of angels, or of evil spirits, souls or shades, embodied in forms so as to admit of description, and yet not subject to the laws of human bodies. Virgil, Tasso, Milton, Klopstock, and many others, have struggled with this difficulty:—no one of them, it will be probably agreed, with any great success; at least, regarding his representation as a hypothesis of a possible form of life, different from all the forms which we know. Yet if we are to reject the laws which govern the known forms of life, in order that we may be able to maintain the possibility of some unknown form in a different planet, we must accept some of these hypotheses, or find a better. We must suppose that weight and cohesion, wounds and mutilations, wings and plumage, would have, either the effect which the poets represent them as having, or some different effect: and in either case it will be impossible to give any sufficient reason why we should confine the population to the surface of a planet. If gravity have not, upon any set of beings, the effect which it has upon us, such beings may live upon the surface of Saturn, though it be mere vapor: but then, on that supposition, they may equally well live in the vast space between Saturn and Jupiter, without needing any planet for their mansion. If we are ready to suppose that there are, in the solar system, conscious beings, not subject to the ordinary laws of life, we may go on to imagine creatures constituted of vaporous elements, floating in the fiery haze of a nebula, or close to the body of a sun; and cloudy forms which soar as vapors in the region of vapor. But such imaginations, besides being rather fitted for the employment of poets than of philosophers, will not, as we have said, find a population for the planets; since such forms may just as easily be conceived swimming round the sun in empty space, or darting from star to star, as confining themselves to the neighborhood of any of the solid globes which revolve about the central sun.
18. We should not, then add anything to the probability of inhabitants on the other planets of our system, even if we were arbitrarily to assume unlimited changes in the laws of nature, when we pass from our region to theirs. But probably, all readers will be of opinion that such assumptions are contrary to the whole scheme and spirit of such speculations as we are here presuming:—that if we speculate on such subjects at all, it must be done by supposing that the same laws of nature operate in the same manner, in planetary, as in terrestrial spaces;—and that as we suppose, and prove, gravity and attraction, inertia and momentum, to follow the same rules, and produce the same effects, on brute matter there, which they do here; so, both these forces, and others, as light and heat, moisture and air, if, in the planets, they go beyond the extremes which limit them here, yet must imply, in any organized beings which exist in the planets, changes, though greater in amount, of the same kind as those which occur in approaching the terrestrial extremes of those elementary agents. And what kind of a population that would lead us to suppose in Jupiter or Saturn, Mars or Venus, the reader has already seen our attempt to determine; and may thence judge whether, when we go so far beyond the terrestrial extremes of heat and cold, light and dimness, vapor and water, air and airlessness, any population at all is probable.
19. Perhaps some persons, even if they cannot resist the force of these reasons, may still yield to them with regret; and may feel as if, having hitherto believed that the planets were inhabited, and having now to give up that belief, their view of the solar system, as one of the provinces of God's creation, were made narrower and poorer than it was before. And this feeling may be still further increased, if they are led to believe also that many of the fixed stars are not the centres of inhabited systems; or that very few, or none are. It may seem to them, as if, by such a change of belief, the field of God's greatness, benevolence, and government, were narrowed and impoverished, to an extent painful and shocking;—as if, instead of being the Maker and Governor of innumerable worlds, of the most varied constitution, we were called upon to regard him as merely the Master of the single world in which we live:—as if, instead of being the object of reverence and adoration to the intelligent population of these thousand spheres, he was recognized and worshipped on one only, and on that, how scantily and imperfectly!
20. It is not to be denied that there may be such a regret and disturbance naturally felt at having to give up our belief that the planets and the stars probably contain servants and worshippers of God. It must always be a matter of pain and trouble, to be urged with tenderness, and to be performed in time, to untwine our reverential religious sentiments from erroneous views of the constitution of the universe with which they have been involved. But the change once made, it is found that religion is uninjured, and reverence undiminished. And therefore we trust that the reader will receive with candor and patience the argument which we have to offer with reference to this view, or rather, this sentiment.
21. We remark, in the first place, that however repugnant it may be to us to believe a state of any part of the universe in which there are not creatures who can know, obey and worship God; we are compelled, by geological evidence, to admit that such a state of things has existed upon the earth, during a far longer period than the whole duration of man's race. If we suppose that the human race, if not by their actual knowledge, obedience, and worship of God, yet at least by their faculties for knowing, obeying, and worshipping, are a sufficient reason why there should be such a province in God's empire; still in fact, this race has existed only for a few thousand years, out of the, perhaps, millions of years of the earth's existence; and during all the previous period, the earth, if tenanted, was tenanted by brute creatures, fishes and lizards, beasts and birds, of which none had any faculty, intellectual, moral, or religious. By the same analogy, therefore, on which we have already insisted, we may argue that there is reason to believe, that if other planets, and other stars, are the seats of habitation, it is rather of such habitation as has prevailed upon the earth during the millions, than during the six thousand years; and that if we have, in consequence of physical reasons, to give up the belief of a population in the other planets, or in the stars; we are giving up, not anything with which we might dwell with religious pleasure—hosts of fellow-servants and fellow-worshippers of the Divine Author of all:—but the mere brute tribes, of the land and of the water, things that creep and crawl, prowl and spring;—none that can lift its visage to the sky, with a feeling that it is looking for its Maker and Master. There have not existed upon the Earth, during the immense ages of its præhuman existence, beings who could recognize and think of the Creator of the world: and if astronomy introduces us, as geology has done, to a new order of material structures, thus barren of an intelligent and religious population, we must learn to accept the prospect, in the one case, as in the other. Nor need we fear that on a further contemplation of the universe, we shall find every part of it ministering, though perhaps not in the way our first thoughts had guessed, to sentiments of reverence and adoration towards the Maker of the universe.
22. The truth is, as the slightest recollection of the course of opinion about the stars may satisfy us, that men have had repeatedly to give up the notions which they had adopted, of the manner in which the material heavens, the stars and the skies, are to minister to man's feeling of reverence for the Creator. It was long ago said, that the heavens declare the glory of God, and the firmament showeth his handiwork: that day and night, sun and moon, clouds and stars, unite in impressing upon us this sentiment. And this language still finds a sympathetic echo, in the breasts of all religious persons. Nor will it ever cease to do so, however our opinions of the structure and nature of the heavenly bodies may alter. When the new aspects of things become familiar, they will show us the handiwork of God, and declare his glory, as plainly as the old ones. But in the progress of opinions, man has often had to resign what seemed to him, at the time, visions so beautiful, sublime, and glorious, that they could not be dismissed without regret. The Universal Lord was at one time conceived as directing the motions of all the spheres by means of Ruling Angels, appointed to preside over each. The prevalence of proportion and number, in the dimensions of these spheres, was assumed to point to the existence of harmonious sounds, accompanying their movements, though unheard by man; as proportion and number had been found to be the accompaniments and conditions of harmony upon earth. The time came, when these opinions were no longer consistent with man's knowledge of the heavenly motions, and of the wide-spreading causes by which they are produced. Then "Ruling Angels from their spheres were hurled," as a matter of belief; though still the poets loved to refer to imagery in which so many lofty and reverent thoughts had so long been clothed. The aspect of the stars was most naturally turned to a lesson of cheerful and thoughtful piety, by the adoption of such a view of their nature and office; and thus, the midnight contemplator of an Italian sky teaches his companion concerning the starry host;
Sit, Jessica; look how the floor of heav'n
Is thick inlaid with patterns of bright gold.
There's not the meanest orb, which thou behold'st,
But in his motion like an angel sings,
Still quiring to the young-eyed cherubims;
Such harmony is in immortal souls.