Inferring and Explaining

ChaPter nIne Testimony In the testimony case a person comes to know something when he is told about it by an eyewitness or when he reads it in the newspaper. . . . No obvious deduc- tive inference leads to a probabilistic conclusion in this case; the acceptance of testimony can be based on two consecutive inferences to the best explanation. . . . First, we would infer that the speaker so testifes because he believes what he says (and not because he has something to gain by so testifying, or because he has gotten confused and has said the opposite of what he means, etc.). Second we would infer that he believes as he does because in fact he witnessed what he described (and not because he has sufered an hallucination, or because his memory deceived him, etc.). —GIlBert harman 1 A Letter of Recommendation I have a good friend in the psychology program. He has asked me to write a letter of recommen- dation in his search for a new job. I know him pretty well—we have collaborated on a short article and have team-taught on two occasions. I tell his prospective employers that he is a fne teacher and a great colleague and that he will go on to be a major fgure in academic psychology someday. Suppose you read my letter and won- der what kind of evidence it provides about the job candidate. Gilbert Harman, in the previous quote, pro- vides a succinct characterization of how infer- ence to the best explanation can be used to unpack the reasoning involved in accepting the word of others. In most cases where we assess testimony, we have more data to explain than simply what has been said. Minimally, we will know something about the speaker and some- thing about the context in which the statement was made. Te abstract model looks something like the following. First of all, we have the infor- mation contained in the language: 79