SCIENTIFIC STUDY OF HUMAN TESTIMONY. 331 



Cooperation of Experts. There are claims that can only be settled 

 by a cooperation of experts, in different branches of science. In regard 

 to the question of the relations of experts to each other in the investi- 

 gations of claims, it is to be observed that a claim should primarily be 

 referred to that specialty that is best capable of dealing with it by de- 

 ductive reasoning. Claims that can be settled by the principles of logic, 

 without the aid of special scientific knowledge such as, from the limi- 

 tations of the human faculties, can never be proved or disproved are 

 to be referred to logicians. If the known principles of any special sci- 

 ence, to which a claim is referred, deductively disprove any claim, it is 

 unscientific for any expert in that science to examine or discuss it, save 

 as an amusement, or for the sake of the incidental facts that an investi- 

 gation may develop. If the claim refer to an open question, the primary 

 expert is to judge whether the cooperation of experts in other branches 

 of science is needed. If the claim belong to a department not yet or- 

 ganized into science the territorial or preexploratory stage in which 

 there are no experts, there are none to decide upon its merits, and the 

 world must remain in ignorance until the experts appear ; but the world, 

 in its impatience and ignorance of logic, practically refers such claims to 

 leaders in various branches of science, or to men of general ability and 

 honesty, who almost always reach erroneous, if not ludicrous, conclu- 

 sions. Such was the origin of the delusions of " animal magnetism," 

 and " odic" and " psychic " force claims that belong to cerebro-physi- 

 ology, a department of science that is now but just passing out of the 

 territorial into the organized stage. 1 When experts blunder, as they 

 may, their conclusions should be revised, not by the people, but by other 

 and better experts. 



II. The reconstructed principles of evidence require that the quality 

 and quantity of evidence necessary for proof of any claim depends on 

 the nature of the claim. 



The principles of evidence that have heretofore commanded the 

 world's acceptance make no distinction in the quality or quantity of 

 testimony for different varieties of claims ; the discovery of a new planet 

 is as credible as the daily rising of the sun ; the introduction of a new 

 force needs no more and no better auspices than the observation of the 



1 Mr. William Crookes, in his kindly and complimentary remarks on my theory of 

 trance, as republished in the London Quarterly Journal of Science, January, 18*78, ob- 

 serves that there may be a physical side to physiological experiments. The suggestion is 

 so far forth a valid one ; the reply is found in the above analysis. The question whether 

 there is in the human body a new and unknown force belongs to cerebro-physiology, and, 

 not being disproved deductively, should be referred to those experts in that specialty 

 who understand how to experiment with living human beings ; and it is for these primary 

 experts to decide whether the experiments they may make require the cooperation of 

 physics, or chemistry, or other branches of science. There may also be a physiological 

 or pathological side to physical experiments; thus the " etheric force" of Mr. T. A. Edi- 

 son was primarily a question of physics, but for its investigation needed and obtained 

 the cooperation of physiologists. 



