Inferring and Explaining

53 Te problem here goes back to the original conditional that set up the experiment in the frst place. Remember the diference between a sound argument and a valid one? Te if . . . then sentence that gets our inference going in the frst place states an absolute connection between the glitch theory and the predicted outcome of the experiment. But the rival explanations we have just considered above seem to show that this connection is not so absolute afer all. Almost always the conditional that sets up our experiment contains what Larry Wright calls a weasel word . Amore modest, but alsomore accu- rate, statement of the predicted experimental outcome will look more like this: If the theory in question is true, then all things being equal we will see . . . in our experiment. We predict that we will observe an as-yet- undiscovered planet at such-and-such location in the night sky, but certainly not if the observa- tory is socked inbyclouds.We expect the solution to turn a certain color in our chemistry experi- ment but not if the test tube is contaminated. Whenwe include this suppressed, but under- stood, ceteris paribus clause, 2 our inference looks a little more problematic. 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, all things being equal , rather than playing them in random order, it will play the most often listened to tracks last. 2. “Essence” and “Right in Time” did not play last. Two valid conclusions can be derived from these premises. One, of course, is that the glitch hypothesis is mistaken. But as a matter of pure logic, it is equally legitimate to infer that all things in our experimental circumstances were not equal. Does any of this mean that the “scientifc method” and the requirement that we experi- mentally test our theories is a waste of time? Nothing could be further from the truth. Let’s go back to our original “evidence” for the glitch theory but add to it the new data from our experiment. new data and exPerImentatIon e 1 . Johnson went to a Pink Martini concert, planning to ask for a specifc encore. e 2 . “Que Sera Sera” was played during the concert. e 3 . He never got a chance to ask for “Lilly.” e 4 . On the ride home the next morning, he set his iPod to play all thirty-six of the Pink Martini songs. e 5 . He set the iPod to “Shufe Songs.” e 6 . He listened to all thirty-six songs. e 7 . The last two songs played were “Lilly” and “Que Sera Sera”—the imagined encore from the night before! e 8 . “Lilly” and “Que Sera Sera” are the two Pink Martini songs he listens to most often. e 9 . When Johnson tried the “shufe all songs” routine for Lucinda Williams, his most listened to songs did not come up last. t 0 . There is a glitch in the iPod software— rather than playing the songs in com- pletely “random” order, it is weighing things according to how often songs are listened to.