Inferring and Explaining

38 InferrIng and exPlaInIng boyfriend was smooching Mary Jane. Holmes had evidence about Watson’s decision about the investment and about what happened at Ridling Torpe Manor. We must decide whether these arguments are any good. Was the evidence for these hypotheses strong? What I am going to call the inference-to-the-best-explanation (IBE) “recipe” is a procedure for answering these kinds of evaluative questions. Inference-to-the-Best-Explanation Recipe 1. Schematize the argument. 2. List some serious (hopefully challeng- ing) rival explanations. 3. Rank order all the explanations—the original along with the rivals. 4. Based on the rank order, see if the origi- nal is the best explanation. If it is, the evi- dence has passed the test and looks pretty good. If it isn’t, it’s failed the test, and the evidence is weak and maybe nonexistent. Let’s frst apply the test or recipe to the simple argument presented in the pop song “Lipstick on Your Collar” that we introduced in chapter 1. Schematizing Connie’s Argument Tat fateful evening at the record hop, Con- nie was confronted with data, mainly her own simple observations, which cry out for expla- nation. Where did the lipstick stain come from? Why was he gone for so long? Why did he say it belonged to her when the stain was red and her lipstick was baby pink? Why when Mary Jane appeared was her lipstick all a mess? Although neither a trained natural scientist nor an experienced detective, Connie easily forms an explanatory hypothesis. When she then writes her sad song, she implicitly asks us to account for what happened. Here’s how I would sche- matize Connie’s evidence for her theory that her boyfriend had been smooching Mary Jane when he lef her alone at the record hop. e 1 . He left Connie all alone at the record hop. e 2 . He was gone for half an hour or more. e 3 . When he returned, there was a lipstick stain on his collar. e 4 . When confronted, he claimed that the stain came from Connie’s lipstick. e 5 . The stain was red. e 6 . Connie’s lipstick was baby pink. e 7 . Mary Jane’s lipstick was all a mess. t 0 . He had been smooching Mary Jane dur- ing the half-hour absence. Rival Explanations (of Connie’s Data) Forourpurposes, rivalexplanations willbeaccounts of the data that fat-out deny the original explana- tion and substitute a completely diferent story of the data ofered as evidence. It will be useful to imagine each truly rival account of evidence as starting out with a lengthy preliminary phrase— “ no, no, no , he was not smooching Mary Jane dur- ing his absence from the record hop; rather . . .” Tis is important because the original explanation might be phrased in very diferent language. t ′ 0 . He and Mary Jane ditched Connie so they could make out. Or an account might ofer a more (or less) detailed account of what happened.