Sui Generis

Those which we call monsters are not so with God, who in the immensity of his work seeth the infinity of forms therein contained. And it may be thought that any figure doth amaze us hath relation unto some other figure of the same kind, although unknown unto man.

…

We call that against nature which cometh against custom. There is nothing, whatsoever it be, that is not according to her. Let therefore the universal and natural reason chase from us the error and expel the astonishment which novelty breedeth and strangeness causeth in us

Montaigne

The stuff about God might not be in the original draft; I haven’t checked. Gide noted that Montaigne’s original drafts were entirely irreligious, but that to pre-empt any chance of heresy, however remote, he later added certain sentences, “like so many lightning-conductors”, to channel away the dangerous attention of the ruling Catholic church.

Regardless of whether this is one of those lightning-conductors, I liked the hypothesis that nothing, however monstrous and accidental-seeming, is completely of its own kind.