SCIENTIFIC STUDY OF HUMAN TESTIMONY. 337 



V. Claims which are absolutely disproved by deductive reasoning, 

 and which therefore the special sciences to which they belong know to 

 be false without any examination. 



Among the more prominent of claims of this kind are those that 

 relate to squaring the circle, flatness of the earth, perpetual motion, 

 including " Keeley " and " Winter " motors, alchemy, astrology, " four 

 dimensions of space," levitation, mind or thought reading, clairvoyance 

 or second-sight, including prevision and retrovision. 



To examine or discuss claims of this kind, for the purpose of deter- 

 mining their truth or falsity, is not only useless, but unscientific. In 

 science there are* three unpardonable sins trusting the senses, non- 

 experts attempting to do the work of experts, and using deduction for 

 induction, or, vice versa, induction when only deduction should be used, 

 as in the class of claims here under consideration. 



The reconstructed principles of evidence explain the following prob- 

 lems in psychology, to which hitherto, so far as I know, no solution has 

 been offered : 



1. Why the logic of the schools has always been on the side of 

 delusions. 



For those who accept non-expert testimony science is the only delu- 

 sion : everything is true except the truth. In the long discussion relat- 

 ing to various modern delusions between Mr. Wallace and Dr. Carpen- 

 ter, Mr. Wallace, according to the rules of evidence, has throughout the 

 best of the argument : his reasoning, for those who trust their senses, 

 who believe that non-experts can do the work of experts, and who use 

 induction when only deduction should be used, is unanswerable. 



Likewise in all, or nearly all, the world's memorable contests be- 

 tween science and delusions, the truth has prevailed, not by virtue of 

 logic, but in spite of it; the instincts of mankind the one saving 

 clause in the constitution of the human brain rising up in their un- 

 conscious majesty, and vindicating their rights and their power against 

 the tyranny of the senses and the cruelty of the syllogism. Logically, 

 Copernicus and Galileo were wrong ; and their accusers, backed by the 

 concurring testimony of the eyes of all mankind through all the genera- 

 tions, have to this hour never been answered. Only on the side of error 

 is there consistency ; during all these recent days, when science sets its 

 forces in array against any dominant delusion, as "animal magnetism," 

 or "odic" force, or "psychic" force, or "spiritualism," it first closes its 

 books of logic and forgets all the teachings of the university. 



2. Why men of culture and genius, and especially of logical attain- 

 ments, are more easily and prof mindly deceived by delusions than men 

 of ordinary ability. 



The history of all delusions, so far as known, establishes the wisdom 

 of the maxim of the father of modern conjurers the famous Houdin : 

 " It is easier to dupe a clever man than a fool." Jugglers, and illusionists, 

 vol. xiii. 22 



