Living Things

Ian Hacking

  • Cognitive Foundations of Natural History: Towards an Anthropology of Science by Scott Atran
    Cambridge, 360 pp, £35.00, August 1990, ISBN 0 521 37293 3

‘War,’ said an old peacenik poster with the words scrawled across a child’s drawing of a tree, ‘is harmful to children and other living things.’ This subtle and sophisticated book has a little of that same power to shock by innocence. It is about how children think of living things, less a matter of what they learn than of what human nature teaches about nature. That is a pleasing picture but not a popular one. Atran is not in search of opponents, but here are a few of the things he is up against ... Every people classifies in its own ways: it is cultural imperialism to expect our sortings of life to be duplicated by others (standard all-purpose cultural relativism). Aristotle was a disaster for biology: he taught that plants and animals should be defined by a priori essences that not only devalued observation but also made it impossible to attend to variations among the species, thereby impeding evolutionary thought for two millennia (textbook history of biology). The taxonomies of natural history are an artwork of the Enlightenment; the Renaissance was mired in a wonderful world of resemblance, natural magic and the doctrine of signatures, whereby plants were the signs of minerals which were the signs of stars (François Jacob, Michel Foucault). The semantics of natural kind terms is such that, when we speak of living things, we are referring, whether we know it or not, to the fundamental kinds at which science aims (Saul Kripke and, sometimes, Hilary Putnam). We have an obligation to integrate our commonsense categories into the best knowledge available; when there is conflict, common sense yields to knowledge (most good scientists, starting with Aristotle).

That is a diverse collection of foes. Aside from the concluding scientism, I don’t suppose that any one person is deeply committed to more than one of those doctrines. I can’t imagine Foucault having cared for rigid designators; the doctrine of signatures is not Kripke’s cup of tea. Do the enemies have anything in common? It is to Atran’s credit that his unified theory makes out that all these baldly summarised assertions are false.

Here’s how it goes. Children have an innate disposition to classify the plants and creatures of the ecosystem. Hence all peoples recognise pretty much the same classes of living things in their locality. We are predisposed to name about six hundred different kinds of life, and to arrange them in a simple taxonomic structure common to all societies, all languages. We come into the world expecting that ‘nature has some basic kinds.’ Classification, moreover, brings with it instant generalisations; we expect all instances of a kind to behave in much the same ways – if you’ve seen one, you’ve seen them all. Everyone acts as if ‘basic kinds have basic natures.’

As for Aristotle, the only part of his biology that was a priori was in effect innate. That is, he took for granted the local classification of six hundred or so living things suitable for his part of the Mediterranean. He wrongly thought that it was almost exhaustive. He aimed at a unified theory of Nature to make sense of his instinctive taxonomy. It would explain why things are what they are: ‘the natures of kinds are to be understood by the place of the kinds in Nature.’ (These mnemonic sentences are mine, not Atran’s.) Individuals are fulfilled only when they reproduce their kind. They should develop as fully as possible according to a template suitable for that kind. Nothing in Aristotle’s theory makes the characteristics of a species eternal or independent of habitat. If the surroundings change, the kinds would have to adapt to fulfil themselves as well as they could in altered circumstances.

Immutable species have a late Renaissance origin. Voyages had begun to bring back a lot of new plants. Cesalpino (1519-1603) had to re-systematise Aristotelian taxonomy to accommodate new kinds. Kinds, once sorted instinctively, now were so plentiful that they needed a general principle to put them in order. He fixed on the seeds, fruits or flowers as the keys to placing plants on a universal taxonomic tree. Local and exotic plants were thus arranged on a timeless scheme. The species were defined by how they reproduced, which in turn entails what Ernst Mayr in the 1960s named the ‘species concept’: a species is a set of individuals that can interbreed.

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