330 THE POPULAR SCIENCE MONTHLY. 



The tests of scientific expertness are distrust of the senses ; the 

 recognition of the relation of induction to deduction ; avoidance of all 

 sources of error, in observation, experiment, or reasoning ; the apprecia- 

 tion of the relative importance and non-importance of real or supposed 

 facts ; the ability to distinguish reality and its semblance, especially 

 between the subjective and the objective ; and, what indeed follows 

 from the other three tests, the maintenance of mental equilibrium dur- 

 ing experimental researches. The reputation of an expert is acquired 

 primarily through other experts, and secondarily through the judgment 

 of mankind. Expertness has its various degrees ; there are experts, 

 and experts, and experts : the highest experts are the originators, the 

 explorers, the pioneers, the founders, the creators of science ; the lowest 

 experts are the followers, the gleaners, the treasurers, the curators of 

 what others have discovered, and who simply repeat and retain the ex- 

 periments of genius. The highest experts the Newtons and Galileos, 

 the Harveys and Jenners of science must stand at first alone, with no 

 other expert at hand, by which to estimate their relative heights and 

 strength ; it is their necessity and their glory to educate experts, by 

 whom their own merits are to be tested ; they must create the standard 

 by which they are to be judged ; their critics will be their own off- 

 spring. For many years Newton was the only man on this planet w r ho 

 understood the theory of gravitation, or was able to criticise it. 



The tests of scientific non-expertness are, blind repose in the senses, 

 the inability to eliminate or appreciate sources of error in observation, 

 experiment, or reasoning; the non-appreciation of the relative impor- 

 tance of real or supposed facts ; the confounding of semblance with 

 reality, and particularly the subjective with the objective ; liability to 

 be entranced, or to have the emotions unduly excited, in the presence 

 of genuine or supposed phenomena ; and the use of induction when only 

 deduction is valid, and vice versa. 



Expertness in one branch of science not only does not qualify, but 

 in various ways may disqualify, one to be an expert in another branch. 



That skill in mathematics unfits one for the successful study of va- 

 rious other specialties was pointed out long ago, both by Abercrombie 

 and Hamilton ; but the antagonism of specialties may be traced, under 

 recent experience, yet more minutely, for it is found that eminence in 

 physics, or chemistry, or astronomy, may thoroughly unfit one for the 

 study of physiology ; and within a few years some of the greatest blun- 

 ders recorded in the history of delusions have been made by naturalists, 

 chemists, physicists, jurists, and astronomers of unquestioned honesty, 

 real genius, and deserved eminence, making, or attempting to make, 

 discoveries in the new and almost unexplored realm of cerebro-physi- 

 ology experiments with living human beings. The worst blunders in 

 the world are scientific blunders the unconscious slips of justly emi- 

 nent men, who do not know that their very eminence in one sphere 

 forbids them to undertake another. 



