When I first dipped my toe tentatively into the frigid waters of psi research, back in the late 1970s, one of the big issues of the time was whether the ability to replicate experiments distinguishes—or as philosophers often say, demarcates—science from non-science (or pseudoscience). This was a big issue because all too often parapsychological skeptics glibly used that demarcation criterion to bludgeon psi researchers and dismiss them as unscientific. Fortunately, in those days there was some very sensible writing on the subject, particularly from Harry Collins, to whom I was especially indebted when I tackled the topic of replicability myself for the first time.1 The skeptical position on the issue of repeatability struck me as so lame that I even naively expected the debate to be settled rather quickly.
However, because psi researchers often enter the field having little acquaintance with the work that preceded them, and because many critics of that research likewise fail to master the relevant issues, I suppose I shouldn’t be surprised that the debate over the nature and importance of replicability still rages. Indeed, little (if any) attention is given to the reasonable points that should have put that issue to rest long ago. Instead, researchers and commentators focus relentlessly—and as usual, inconclusively—on the results of meta-analyses. Some of those meta-analyses are indeed worthy of attention,2 but (I would say) only in light of the overlooked considerations I discuss below.
So I’d like to review some problems with the still-widely–held view that the ability to replicate experiments is what demarcates science from non-science or pseudoscience. As I see it, that position is both shallow and confused, and the problems with it don’t even have the virtue of being subtle. First, the skeptical reliance on the demarcation criterion rests on a naïve conception of the actual importance within science of experimental repeatability. Indeed, experimental repeatability plays little if any role in disciplines (including some physical sciences) whose scientific credentials are not in dispute. Second, it seriously misconstrues how the appeal to replicability works even in those physical sciences where it plays a real role. Third, the received view rests on philosophical confusions regarding the nature of similarity—in particular, the flawed idea that there can be formal, context-independent, criteria for the similarity of two things. And fourth, it rests on confusions over the nature of human abilities generally, and in particular, the appropriate methodologies for studying them. One could also argue that a fifth problem for this received view is that psi research can in fact point to replicable results. But that last issue must be reserved for another occasion.
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