SELECTION AND EXPLANATION

Abstract

Explanations appealing to natural selection have an unusual and prima facie paradoxical feature. While we may explain general truths using such explanations, those explanations do not transfer to the particular instances of those general truths. Thus natural selection and the selective advantage of speed in escaping predators can explain why healthy, normal, adult gazelles can run fast. Yet such an explanation does not explain why any particular gazelle can run fast—the explanation in individual cases would appeal to the physiology of the animal, in particular its musculo-skeletal structure and heart and lung capacity and so forth. This contrasts with an explanation of why diamonds are hard, which does transfer to individual diamonds. The reason why all diamonds are hard is the same reason why any particular diamond is hard. Such explanations one might call ‘particularizable’. Explanations appealing to natural selection are not particularizable. In this paper I aim to isolate the source of the difference in the two kinds of explanation and thereby resolve the apparent paradox in the case of selection explanations. While the interest in such explanations stems from their use in evolutionary biology, the feature referred to is not limited to biological explanations alone. Any selection explanation has the property of not being particularizable, and it will be helpful in this paper to focus on a non-biological example. A restaurant has a rule that no gentleman will be admitted who is not wearing a tie. We may imagine that the rule is newly introduced and that potential customers do not know about it— and so the rule itself does not influence the wearing of ties on the particular evening we are considering. So it is true on this evening that all the men in the restaurant are wearing ties. And the explanation is a selection one. Many men wanted to dine in the restaurant; only those wearing ties were admitted; the tieless were sent away. But this explanation of the general proposition, that all the men are wearing ties, does not explain why any individual diner is wearing a tie. Mr Grey has just come from his office and is wearing the suit and tie he wears for work; Colonel Black is a very formal gentleman who always wears a tie; Dr White is trying to impress his new date, etc.. So the selection explanation of the general proposition is not particularizable.