Inferring and Explaining

144 InferrIng and exPlaInIng likely to be true? Does it provide a good strategy for determining the truth? But inference to the best narrative invites a third challenge. Does it even make sense to talk about truth in contexts involving violent ex-husbands or constitutional success or failure? All three of these challenges must be addressed, if not defnitively answered. Gilbert Harman foresaw Glass’s frst chal- lenge in his initial treatment of inference to the best explanation. Tere is, of course, a problemabout how one is to judge that one hypothesis is sufciently better than another hypothesis. Presumably such a judgment will be based on considerations such as which hypothesis is simpler, which is more plausible, which explains more, which is less ad hoc, and so forth. I do not wish to deny that there is a problem about explaining the exact nature of these considerations; I will not, however, say any- thing more about this problem. 3 One might ask why is there is any problem in the frst place. Harman seems to answer his own question about explanatory virtue.Te best explanation must be determined by the stan- dards of simplicity, plausibility, completeness, and not being ad hoc. Te superfcial answer is obvious. His list of explanatory virtues is incom- plete (“and so forth”), the virtues can work against one another—the simplest account may not be themost complete—and each one is vague and overly general. Just as with inference to the best explanation, we face the obvious question of what are the criteria for one narrative to be better than another. Here, I thinkHarman’s little checklist, however vague, is helpful. Te better narrative will be the one that best exemplifes the following characteristics: • It will tend to provide the most complete story. • It will tend to provide the simplest story. • It will provide the most plausible story. • It will provide the least ad hoc story. But feshing out these criteria for explanatory and narrative success is clearly unfnished busi- ness in the philosophy of science andnarratology. As serious as this problem clearly is, I don’t believe that it is as serious as the skeptics make it out to be. I know how to speak, understand, read, and write English. I know that the Eng- lish sentence “Colorless green ideas sleep furiously,” though nonsensical and probably self-contradictory, is grammatically correct. According to a dominant tradition in Western epistemology, if I am right about my linguistic skills, I should be able to plainly articulate the rules I have used to recognize the grammatically of the green ideas sentence. Obviously, every speaker of a language has mas- tered and internalized a generative grammar that expresses his knowledge of his language. Tis is not to say that he is aware of the rules of the grammar or even that he can become aware of them. 4 Chomsky concedes that the rules of this genera- tive grammar may be cognitively inaccessible and certainly difcult to articulate. Jason Stan- ley vigorously demurs: Knowing how to do something is the same as knowing a fact. It follows that learning how to do something is learning a fact. For example, when you learned how to swim, what happened is that you learned some facts about swimming. . . . You know how to perform