Then came the Snake.
What the Snake Said
‘I have here,’ the Snake said, ‘some stuff that will no doubt strike you, in your Innocence, as a sample of bona fide, original, straight off the shelf, X-ness. But come a little closer—come close enough to see how the stuff is puttogether—and you’ll see that it isn’t X after all. In fact, it’s some kind of Y
—‘Sucks to how it’s put together,’ we replied, in our Innocence. ‘For a thing to strike us as of a kind with paradigm Xs just is for that thing to be an X. X-ness just is the property of being the kind of thing to which we do (or would)extrapolate from appropriate experience with typical Xs. Man is the measure; vide doorknobs.’
—‘That,’ the Snake replied, ‘depends. Since we’re assuming from the start that Xs and Ys are, for practical purposes, indistinguishable in their effects on you, it follows that thinking of both Xs and Ys as Xs will do you no practical harm.For example, for purposes of longevity, reproductive efficiency, and the like, it’s all one whether you ingest only Xsunder the description ‘X or you ingest both Xs and Ys under that description. But that is ingest; I am in earnest. Ifyou want to carve Nature at the joints, if you want to know how the world seems to God, you will have to learn sometimesto distinguish between Xs and Ys even though they taste (and feel, and look, and sound, and quite generally strike youas) much the same. It’s entirely up to you of course. Far be it from me to twist your arm. (Sign here, please. In blood.)’
We fell for that, and it was, on balance, a fortunate Fall. The trouble with being Innocent is that, although how God made things sometimes shows up in broad similarities and differences in the way that they strike us (trees reliably strikeus as quite different from rocks; and they are), sometimes it only shows up in similarities and differences in the waythings
strike us in very highly contrived, quite unnatural environments; experimental environments, as it might be. For it’s sometimes only in terms of a taxonomy that classifies things by similarities and differences among the ways that theydo (or would) behave in those sorts of environments, that we can specify the deep generalizations that the world obeys.We are, after all, peculiar and complicated sorts of objects. There is no obvious reason why similarity in respect of theway that things affect us should, in general, predict similarity in the way that they affect objects that are less peculiarthan us, or less complicated than us, or that are peculiar and complicated in different ways than us.36
Unless, however, we contrive, with malice aforethought, that things should strike us as alike only if they are alike in respect of the deep sources of their causal powers: that they should strike us as alike only if they share their hiddenessences. So, for example, we can set things up so that the chemicals in the bottles will both turn the paper red (andthereby strike us as similar) if, but only if, they are both acids. Or, we can set things up so that both meters will registerthe same (and thereby strike us as similar) if, but only if, there’s the same amount of current in both the circuits; and soon. The moral is that whereas you lock to doorknobhood via a metaphysical necessity, if you want to lock to a natural kindproperty, you have actually to do the science.
So much for the fairy tale. It’s intuitively plausible, phylogenetically, ontogenetically, and even just historically, to think of natural kind concepts as late sophistications that are somehow constructed on a prior cognitive capacity forconcepts of mind-dependent properties. But intuitively plausible is one thing, true is another. So, is it true? And, whatdoes “doing the science” amount to? How, having started out as Innocents with no concepts of natural kinds, could wehave got to where we are, with natural kind concepts like WATER? I turn to these questions in, more or less, thatorder.