British Academy: The UK's National Academy for the Humanities and Social Sciences
Enquiry, Evidence and Facts: An Interdisciplinary Conference
Alien Abduction: Inference to the Best Explanation and the Evaluation of Testimony
Professor Peter Lipton
University of Cambridge, Head of Department of History and Philosophy of Science
Free School Lane, Cambridge, CB2 3RH
Biography
Peter Lipton received his BA from Wesleyan University and his BPhil and DPhil from Oxford University. He taught in the States at Clark University and Williams College, and is currently Hans Rausing Professor and Head of the Department of the History and Philosophy of Science at Cambridge University and a Fellow of King's College. He is Fellow of the Academy of Medical Sciences and a member of the Nuffield Council on Bioethics. Philosophical interests include the structures of explanation and inference in science, the nature of scientific progress, social epistemology, the relation between science and religion, and biomedical ethics. He is the author of Inference to the Best Explanation (2nd edition, Routledge, 2004) and was the 2004 Medawar Prize Lecturer of the Royal Society. He is a founding panelist on AskPhilosophers.org.
Selected publications are available at: http://www.hps.cam.ac.uk/dept/lipton.html
Abstract
Most of the evidence we have is second-hand, based on the testimony of others. We need to determine when to believe what we are told, which is to say that we need ways of deploying evidence about evidence. I explore the prospects of applying inference to the Best Explanation (IBE – sometimes also known as ‘abduction’) to an account of the way we decide whether to accept the word of others (sometimes known as ‘aliens’). IBE is a general account of non-demonstrative or inductive inference, but it has been applied in a particular way to the management of testimony. The governing idea of Testimonial IBE (TIBE) is that a recipient of testimony (‘hearer’) decides whether to believe the claim of the informant (‘speaker’) by considering whether the truth of that claim would figure in the best explanation of the fact that the speaker made it.
The talk is in five parts. The first introduces the general idea of IBE as an account of many non-demonstrative inferences. I distinguish actual from potential and likeliest from loveliest explanation, and underscore the challenges of identifying the explanatory virtues, of showing that they coincide with inferential virtues, and of showing that the former are in fact our guide to the latter.
The second part offers some general remarks on the epistemology of testimony. I emphasise the ubiquity of our reliance on testimony and the challenge of deciding whether we should believe what we are told. I sketch a default-trigger model, according to which we only go into inferential mode when some aspect of the testimony keeps us from simply accepting what we are told, and I then focus my attention on the problem of describing how the inferential process works in the triggered cases. What is involved is often a second-order inference about the reliability of the speaker’s first-order inference, where one of the challenges is to assess this reliability without evading the issue of testimony altogether by simply finding out independently whether what the speaker said was true.
The third part suggests how IBE could be used to account for this process of testimonial discrimination, the idea of TIBE. The governing thought is that the hearer considers what would be the best explanation of a distinctive datum: the speaker’s utterance. Would the best explanation of why the speaker said P include P itself? The question is whether the fact uttered would be part of the best explanation of the fact of utterance.
The fourth part addresses the objection that TIBE is trivial. Put negatively, the question is whether there is any forms of inference concerning the acceptability of testimony that the TIBE account would exclude. I suggest that there are, contrasting TIBE with some accounts that appeal to evidence that is independent of the testimonial episode, that appeal the speaker’s track record, or that appeal to the speaker’s status.
In the final part of the talk I consider the worry that if it is not trivial, TIBE is false. In particular, I worry about evidence that is not explained, explanations that do not entail the truth of the testimony, and inferential role of background belief.