Inferring and Explaining

52 songs, “Right in Time” and “Essence,” the most. So if I set my iPod to play all her tracks and to shufe them, I am predicting that the two songs will be played last. Suppose I do all this with my iPod and listen to all her songs—more than a hundred, I’d say. We can imagine four diferent outcomes to the experiment. Focusing on the last two songs, we might observe any of the following. 1. If the theory is true, we will see . . . in the experiment. 2. We see . . . in the experiment. 3. The theory is true. Options e n c and e n d are interesting and deserve further study, but let’s set them to the side and e n a . The two songs come up as the last two played. e n b . Neither song is in the last two. e n c . Only “Right in Time” is in the last two. e n d . Only “Essence” is in the last two. 1. If the theory is true, we will see . . . in the experiment. 2. We do not see . . . in the experiment. 3. The theory is not true. Experiments, according to the pretty picture, provide tests that can show us that theories are false. Tey cannot, however, show us that theo- ries are true. Remember, it is a fallacy to afrm the consequent. InferrIng and exPlaInIng A Better, But Untidy, Picture of Scientifc Disconfrmation Now, the theory about the iPod hardly counts as deeply scientifc, but suppose we imagine an experiment nonetheless.Te conditional that sets all this up looks something such as the following: focus on the “pure” experimental outcomes. According to the pretty picture, e n b conclusively establishes that the glitch theory is false. But isn’t that a little extreme? We’ve already honed our skills at rival explanations—surely we can imagine scenarios where the glitch hypothesis is (was) true but neither song played last. 1. If there is a glitch in the software, so that when the iPod is set to play all the songs by an artist and is set to “shufe” these songs, then rather than playing them in random order, it will play the most often listened to tracks last. I could test my theory by reprogramming every- thingwith the PinkMartini tracks, but since I’ve ofered a general theory, let’s test it with a dif- ferent artist. I have lots of Lucinda Williams’s albums, and I’m certain I listen to two of her t 1 . Between the drive home and the experiment, iTunes downloaded a newer (debugged) version of the software. t 2 . The glitch only occurs in playlists shorter than ffty songs. t 3 . There is a countervailing glitch when any of the songs are classifed as “country.” It’s doubtful in the extreme that a negative experimental outcome can falsify a theory, though it certainly can provide strong evidence that there is something wrong with the theory.