C. D. Broad
I will begin this paper by stating in rough outline what I consider to be the relevance of psychical research to philosophy, and I shall devote the rest of it to developing this preliminary statement in detail.
In my opinion psychical research is highly relevant to philosophy for the following reasons. There are certain limiting principles which we unhesitatingly take for granted as the framework within which all our practical activities and our scientific theories are confined. Some of these seem to be self-evident. Others are so overwhelmingly supported by all the empirical facts which fall within the range of ordinary experience and the scientific elaborations of it (including under this heading orthodox psychology) that it hardly enters our heads to question them. Let us call these Basic Limiting Principles. Now psychical research is concerned with alleged events which seem prima facie to conflict with one or more of these principles. Let us call any event which seems prima facie to do this an Ostensibly Paranormal Event.
A psychical researcher has to raise the following questions about any ostensibly paranormal event which he investigates. (1) Did it really happen? Has it been accurately observed and correctly described? (2) Supposing that it really did happen and has been accurately observed and
Reprinted from Philosophy, volume 24 ( 1949), pp. 291-309, by permission of the Cambridge University Press.