The careful study of this book is of the greatest value as an exercise in the criticism of evidence and as a guide for anyone who proposes to study such matters at first hand.
I do not think that I can illustrate my meaning better than by a description of my own impressions in connection with the book.
When I first read it I was much impressed by the scientific eminence of those who bore witness to the authenticity of the events described.
I reflected that here we had a Physicist of no mean order, assisted by other scientists of European reputation, men trained, presumably, in the art of exact observation and not likely to be deceived by the manipulations of a conjuror. Surely we must believe their testimony if we are to assign any value to human evidence at all!
Then, as I thought over the matter more and became more convinced of the importance of the conclusions to be drawn from these experiments, if genuine, I felt that these considerations, although possessed of their own importance, were yet not sufficient to warrant acceptance of the evidence without careful examination of the intrinsic qualities of the latter.
On further study of the book I was struck by the fact that not one of the special experiments, carefully designed by Zöllner to establish the genuineness of the phenomena and the validity of the four-dimensional explanation beyond all doubt, had succeeded. This was suspicious, although not, of course, conclusive. Specially devised test experiments may very likely fail simply because they may involve the upsetting of some essential condition which is not fully understood by the experimenter. But when such experiments fail, while others of, apparently, identical general nature succeed, it gives one cause for thought.
Finally, when I came to examine the records of individual experiments in the light of the criticisms of Mr. Carrington, of Dr. Hyslop and others, I realised that the nature of the evidence was emphatically not good enough to justify our accepting as demonstrated the facts which Zöllner claimed to have established.
I shall not waste my own time and that of the reader by giving numerous instances of the sort of thing I mean.
I will confine myself to the case that we are more especially considering as being typical of the whole of this class of phenomena, i.e., the case of the removal of a coin from a closed and fastened box.