But what is this vegetation and generation of which you talk? said DEMEA.  Can you explain their operations, and anatomise that fine internal structure on which they depend?

As much, at least, replied Philo, as cleanthes can explain the operations of reason, or anatomise 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 excusable:  But reason, in its internal fabric and structure, is really as little known to us as instinct or vegetation; and, perhaps, even that vague, indeterminate 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?