752 THE POPULAR SCIENCE MONTHLY. 



Among this class of scientific blunders is the custom of applying 

 the calculations of chances to experiments with living human beings. 

 Thus in the now well-known mind-reading performances it was averred 

 that by a mathematical calculation there would be but one chance in 

 several hundred thousand of finding any object in a house or hall or 

 assemblage ; hence it was inferred that a new force, or manifestation of 

 force, had been revealed to the world. The fallacies in this philosophy 

 do not require a very long search ; of the many objects in any house, or 

 indeed in any public building, but a small minority would be accessible 

 in any mind-reading test, and of these few only a limited number are 

 of a sufficiently positive nature and description to be thought of by the 

 subject of such experiments 5 then, in addition, are all the errors that 

 come from intentional and unintentional assistance of audiences and by- 

 standers. 



Practically the only way to eliminate, in a scientific manner, the 

 error of chance or coincidence in all experiments of that character, is by 

 making comparative experiments in the same line, with all the sources 

 of error closed except chance, and to repeat these a sufficient number 

 of times to make an absolute domonstration. In this way it was shown 

 that mind-reading, so called, was really muscle-reading. In these and 

 in all studies of like character it is to be recognized that coincidences 

 of the most extraordinary and astonishing nature are liable to occur at 

 any instant, and that they are as likely to occur on the first trial as on 

 the last of a long series. To deterRiine whether any conjunction of 

 events is simple coincidence, or the result of some new fact or law in 

 science, is possible oftentimes only through a series of comparative ex- 

 periments. In the researches which I made in muscle-reading it was 

 shown over and over that by pure chance alone — every other element 

 of error being excluded — the blindfold subject would, under certain 

 conditions, find the object looked for in* one case and sometimes in two 

 cases out of twelve. 



It would seem that the errors from chance and coincidence were the 

 most patent of all the errors that complicate and confound scientific in- 

 vestigation, and so clear even to the unskilled and unthinking mind, that 

 trained investigators would never be deluded by them. But in practice 

 it vitiates the research and the philosophizing of educated men, even more 

 perhaps than any other of the six, excepting the involuntary action of 

 mind on body which, as we have seen, has been the stone of stumbling 

 for physiologists ever since physiolog;f was introduced into science. 



Hay-fever, for half a century and more, has supplied an unusual 

 richness of material for false reasoning of a similar type. An English 

 physician, a victim of this disorder, notices that he is worse as he 

 crosses a field of grass, and concludes that at last he has found the one 

 source of the mystery, and so gives the affection a misleading name 

 which it can never lose ; Helmholtz, a leader both in physics and physi- 

 ology, puts the nasal secretions under the microscope, discovers some 



