Inferring and Explaining

20 InferrIng and exPlaInIng exciting in its own right. Most of you, however, should see it as a necessary means to an end. I assume most of you care about whether scien- tists know what they are talking about. If you are like I am, you think they probably do. But to really feel confdent about this, you need to have some answers to the philosophical skeptic who says it might all be a dream and the proce- dural skeptic who argues from a specifc model of scientifc knowledge to doubt about things such as evolution and climate change. To answer either of these skeptics productively, you need some agreement about the nature of knowledge. Knowledge and Belief Human beings seem to be a very credulous spe- cies; we believe an amazing variety of things. Our ancestors believed inwitches, that the earth was fat, and in the divine right of kings. People today believe that their futures are foretold in horoscopes, that good writing can be accom- plished in frst drafs, and that their favorite sports teamwill fnally get it together. From the perspective of history, it is easy to fnd countless beliefs that we sincerely held that strike us as foolish, dangerous, and immoral. But of course, not all beliefs ft into this category. Other things we don’t merely believe, we know. I, of course, believe that I am a philoso- phy professor, a one-time sofball player, and a husband to a beautiful woman. But I don’t just believe these things, I know them. Te dis- tinction between belief and knowledge is not like the one between being a sibling and being an only child—it is not an exclusive, either/ or diference. It is rather like the distinction between an automobile and a convertible. To be a convertible is to be a special kind of automo- bile. As logicians put it, being an automobile is a necessary condition of being a convertible. Not all automobiles are convertibles, but all convert- ibles are automobiles. Traditional models, or defnitions, of knowl- edge have attempted to articulate a list of nec- essary conditions that are jointly sufcient for having genuine knowledge. Te abstract noun knowledge is kind of artifcial. I think we will do better to use the more familiar verb. Our obser- vations about knowing and believing suggest the frst entry on our list of necessary conditions: J knows P only if: i. J believes P . Tere is a fairly common way of talking that seems to call this into question. Suppose we have a friendwho is headed for heartache partly because he refuses to take seriously the obvious evidence of his lover’s infdelity. We might say, “Jake knows that she’s untrue, but he can’t bring himself to believe it.” Or perhaps we have a col- league who is foolishly refusing to take heed of medical symptoms: “Sarah knows something is wrong but just won’t believe it.” How seriously should we take the claim that both Jake and Sarah have knowledge but lack belief? Not very. Jake sees the obvious signs and has his moments of doubt. Sarah too. If they didn’t, we wouldn’t be inclined to say they knew. It is, of course, possible for people to be perversely dense. People can be totally oblivious to things that are perfectly obvious to others. Connie may genuinely believe that her lover is totally faith- ful despite the lame excuses and the lipstick on his collar. But we would never be tempted to say