Inferring and Explaining

54 InferrIng and exPlaInIng We’ve already imagined some rivals to e 9 , but I assume that you would all agree with me that t 0 has been seriously weakened by our experi- ment and that the random fuke hypothesis or the operator error rivals look even better. Te moral here is straightforward. When a theory suggests that we can expect to see some- thing as yet undiscovered andwe go out and look for this thing but don’t fnd it, this is highly rel- evant new data that almost always hurts the sta- tus of the original explanation as being the best explanation of everything, including, of course, the experimental results. A Better, But Untidy, Picture of Scientifc Confrmation None of what I have just told you is earthshak- ing nor is it unknown by careful scientists and philosophers. Still, the pretty picture, partly because it is so pretty, can allow us to lose sight of the subtleties of experimental design and protocol. Maybe even more problematic for the pretty picture is the evidential value of experi- mental confrmation. Suppose I program my iPod to play all 116 Lucinda Williams tracks. I set the iPod to shuf- fe the songs and then sit back for a really long time and wait to see what the last two songs are. Sure enough, up pops “Essence” and “Right in Time” as the last two played. What do you think of my glitch hypothesis now? According to the pretty picture, my theory has been put to the test and perhaps surpris- ingly, has survived the test. But it would be the fallacy of afrming the consequent to say that the experiment has confrmed my theory. We’ve already seen that if confrmation means “logically derived” from the experimental setup and results, that’s exactly right. But none of this means that the experiment hasn’t produced very strong evidence that the songs are not playing in purely random order. 3 What is the best explanation of e 1 through e 8 when we add the positive experimental result below? e 9 . When Johnson tried the “shufe all songs” routine for Lucinda Williams, his most lis- tened to songs did indeed come up last. All the rivals we thought of with Pink Martini are still possible, but hardly any seem plausible any longer. One of themost seriouslymisleading features of the pretty picture is that it sets up an asymmetry between experimental confrmation and disconfrmation. We’ve seen why as a mat- ter of deductive logic this asymmetry exists. But no such asymmetry exists when we see experi- mental results as additional data that the tested theory and its rivals must explain. The Signifcance of New Data One of the remarkable things about the natural sciences is that we can devise experiments and go looking forhighlyrelevantnewdata. Butnewdata can cause us to rethink our evidence or feel even more confdent about it in any of the arguments we’ve been thinking about, not just the scientifc ones. If we fnd out that Dick’s been in the hospi- tal with pneumonia and that he loaned his car to his buddy, Sam, things are going to seem much more promising for Dick and Jane. And if we fnd a copy of Sarah’s midtermon Charlie’s laptop, the case for cheating is obviously strengthened.