There are two possible replies that Quine may wish to advance in response to the inferential gap question. He may simply, and stubbornly, maintain that such questions are no longer relevant once we dispense with first philosophy. However, it is not immediately clear that giving up the quest for a justification of science means that all normative questions regarding inferences are therefore irrelevant. Quine's second option would be to provide a normative description of what justifies our theoretical inferences, but from a naturalistic perspective.
Which of these options Quine himself would opt for is not clear since on separate occasions he seems to make statements suggestive of both possible replies. However, in what follows I will take the second line of response (if only because doing so would make for a much more interesting post). To wit, I will argue in favour of a normative, and yet naturalistic, description of our inferences from evidence to theory. The starting point for just such a normative description is alluded to by Quine himself: "Again there is the area [called] evolutionary epistemology [that] shows how some structural traits of perception could have been predicted from survival value."[Quine (1994), 30]
Defenders of traditional epistemology emphasise that epistemology is not only concerned with which belief forming mechanisms are truth-conducive, but also with why they are truth-conducive. Hence, an adequate naturalistic account of knowledge should provide no less. The naturalistic response to this challenge is an evolutionary epistemology that explains justified belief in terms of natural selection. On this view, nature has endowed us with cognitive mechanisms and epistemic practices that are biased towards truth. The underlying assumption here is that natural selection isolates and preserves those belief-forming mechanisms that are truth-conducive. Creatures with belief forming mechanisms that are generally not truth-conducive fair very poorly in the evolutionary struggle and eventually go extinct. If nature has constructed us so that we are biased towards truth, then the best means at arriving at truth is to use the very cognitive mechanisms nature has given us. Thus, evolutionary epistemology's investigation into our use of induction and our reliance on our perceptual mechanisms turns out to be not merely a descriptive but also a normative endeavour. In brief, had our belief forming mechanisms not been generally truth-conducive (as the sceptic fears) we would not even be around to talk about them.
Jack Crumley raises two objections to the above evolutionary account of epistemic justification. Crumley notes that the evolutionary argument depends on the assumption that natural selection favours mechanisms that are generally truth conducive. However, he points out that false beliefs may often have survival value. For instance, erring on the side of caution may often prove be of greater survival value than an even-handed assessment. To wit, the individual that ran away every time the bush rustled because she assumed that there was a lion in the bushes may fair better than her pathetic, yet epistemically more praiseworthy, companion who sticks around to investigate. Secondly, Crumley notes that it is questionable that many of our scientific beliefs contribute to our survival. Thus, he remarks poignantly: "Nature seems, at best, indifferent to whether we truly believe that quarks have flavours."[Crumley (1999), 203]
In my next post on this topic I will respond to Crumley’s objections.
Jack Crumley, An Introduction to Epistemology. (California: Mayfield Publishing Co., 1999).