Richard G. Swinburne, Emeritus Professor of Philosophy, University of Oxford, gives a talk for the New Insights and Directions for Religious Epistemology seminar series.
Abstract: Epiphenomenalism is the scientific theory that conscious events never cause physical events (and so intentions never cause brain events). The Libet programme seeks to prove epiphenomenalism by showing that it never makes any difference to a sequence of brain events whether or not an intention occurs during the course of it. To show that, it needs to show when (relative to brain events) some intention occurs; and to show that it relies on the reports of subjects about when and whether they form any intention. But while we are always justified in believing claims based on apparent experience, memory, or testimony in the absence of defeaters, it is a defeater to any such claim that some event occurred, that the apparent experience, memory, or testimony was not caused by the event. So we would only be justified in believing these reports if we were justified in believing that the reports were caused by subjects' having an intention to make words come out of their mouths which correctly report their other intentions. So the programme to prove epiphenomenalism relies on evidence about subjects' intentions on which it would only be justified in relying if epiphenomenalism is false. Hence the programme is self-defeating; and so is any other programme purporting to show that we can have a justified belief in epiphenomenalism and so in the causal closure of the physical.