Pray open up this argument a little farther, said Demea, for I do not rightly apprehend it in that concise manner in which you have expressed it.
Our friend Cleanthes, replied Philo, as you have heard, asserts, that since no question of fact can be proved otherwise than by experience, the existence of a Deity admits not of proof from any other medium. The world, says he, resembles the works of human contrivance; therefore its cause must also resemble that of the other. Here we may remark, that the operation of one very small part of nature, to wit man, upon another very small part, to wit that inanimate matter lying within his reach, is the rule by which Cleanthes judges of the origin of the whole; and he measures objects, so widely disproportioned, by the same individual standard. But to waive all objections drawn from this topic, I affirm, that there are other parts of the universe (besides the machines of human invention) which bear still a greater resemblance to the fabric of the world, and which, therefore, afford a better conjecture concerning the universal origin of this system. These parts are animals and vegetables. The world plainly resembles more an animal or a vegetable, than it does a watch or a knitting-loom. Its cause, therefore, it is more probable, resembles the cause of the former. The cause of the former is generation or vegetation. The cause, therefore, of the world, we may infer to be something similar or analogous to generation or vegetation.
But how is it conceivable, said Demea, that the world can arise from any thing similar to vegetation or generation?
Very easily, replied Philo. In like manner as a tree sheds its seed into the neighbouring fields, and produces other trees; so the great vegetable, the world, or this planetary system, produces within itself certain seeds, which, being scattered into the surrounding chaos, vegetate into new worlds. A comet, for instance, is the seed of a world; and after it has been fully ripened, by passing from sun to sun, and star to star, it is at last tossed into the unformed elements which every where surround this universe, and immediately sprouts up into a new system.
Or if, for the sake of variety (for I see no other advantage), we should suppose this world to be an animal; a comet is the egg of this animal: and in like manner as an ostrich lays its egg in the sand, which, without any farther care, hatches the egg, and produces a new animal; so ... I understand you, says Demea: But what wild, arbitrary suppositions are these! What data have you for such extraordinary conclusions? And is the slight, imaginary resemblance of the world to a vegetable or an animal sufficient to establish the same inference with regard to both? Objects, which are in general so widely different, ought they to be a standard for each other?
Right, cries Philo: This is the topic on which I have all along insisted. I have still asserted, that we have no data to establish any system of cosmogony. Our experience, so imperfect in itself, and so limited both in extent and duration, can afford us no probable conjecture concerning the whole of things. But if we must needs fix on some hypothesis; by what rule, pray, ought we to determine our choice? Is there any other rule than the greater similarity of the objects compared? And does not a plant or an animal, which springs from vegetation or generation, bear a stronger resemblance to the world, than does any artificial machine, which arises from reason and design?
But what is this vegetation and generation of which you talk, said Demea? Can you explain their operations, and anatomize that fine internal structure on which they depend?
As much, at least, replied Philo, as Cleanthes can explain the operations of reason, or anatomize that internal structure on which it depends. But without any such elaborate disquisitions, when I see an animal, I infer, that it sprang from generation; and that with as great certainty as you conclude a house to have been reared by design. These words, generation, reason, mark only certain powers and energies in nature, whose effects are known, but whose essence is incomprehensible; and one of these principles, more than the other, has no privilege for being made a standard to the whole of nature.
In reality, Demea, it may reasonably be expected, that the larger the views are which we take of things, the better will they conduct us in our conclusions concerning such extraordinary and such magnificent subjects. In this little corner of the world alone, there are four principles, reason, instinct, generation, vegetation, which are similar to each other, and are the causes of similar effects. What a number of other principles may we naturally suppose in the immense extent and variety of the universe, could we travel from planet to planet, and from system to system, in order to examine each part of this mighty fabric? Any one of these four principles above mentioned, (and a hundred others which lie open to our conjecture), may afford us a theory by which to judge of the origin of the world; and it is a palpable and egregious partiality to confine our view entirely to that principle by which our own minds operate. Were this principle more intelligible on that account, such a partiality might be somewhat excuseable: But reason, in its internal fabric and structure, is really as little known to us as instinct or vegetation; and, perhaps, even that vague, undeterminate word, Nature, to which the vulgar refer every thing, is not at the bottom more inexplicable. The effects of these principles are all known to us from experience; but the principles themselves, and their manner of operation, are totally unknown; nor is it less intelligible, or less conformable to experience, to say, that the world arose by vegetation, from a seed shed by another world, than to say that it arose from a divine reason or contrivance, according to the sense in which Cleanthes understands it.
But methinks, said Demea, if the world had a vegetative quality, and could sow the seeds of new worlds into the infinite chaos, this power would be still an additional argument for design in its author. For whence could arise so wonderful a faculty but from design? Or how can order spring from any thing which perceives not that order which it bestows?