71 



plants were changed at will, by supplying to their surrounding 

 medium various substances. It was easy to obtain definite 

 results, and it was natural to conclude that the chemical structure 

 of these particular substances produced the result, and our pre- 

 scription was narrowed to certain substances. Later it was 

 discovered that the results are not due to the chemical nature 

 of the substances, but to a physical condition developed by their 

 presence, a condition which may be developed by other sub- 

 stances or by no substances, and so our prescription was much 

 enlarged." 



Professor Coulter calls attention to the fact that the "pre- 

 vailing belief among the untrained is that any result may be ex- 

 plained by some single factor operating as a cause. They seem 

 to have no conception of the fact that the cause of every result is 

 made up of a combination of interacting factors, often in numbers 

 and combinations that are absolutely bewildering to contem- 

 plate." Though it is fortunate when leaders, as in public opinion, 

 "have gotten hold of one real factor," this habit of "considering 

 only one factor, when perhaps many are involved, indicates a 

 very primitive and untrained condition of mind." 



Third, this spirit keeps one close to the facts. "There seems 

 to be abroad a notion that one may start with a single w^ell- 

 attested fact, and by some logical machinery construct an elabo- 

 rate system and reach an authentic conclusion, much as the world 

 has imagined that Cuvier could do if a single bone were fur- 

 nished him. The result is bad, even though the fact may have 

 an unclouded title. But it happens too often that great super- 

 structures have been reared upon a fact which is claimed rather 

 than demonstrated. Facts are like stepping stones; so long as 

 one can get a reasonably close series of them he can make some 

 progress in a given direction, but when he steps beyond them he 

 flounders. As one travels away from a fact its significance in 

 any conclusion becomes more and more attenuated, until pres- 

 ently the vanishing point is reached, like the rays of light from 

 a candle." 



Such 'vain imaginings' are "delightfully seductive to many 

 people, whose life and conduct are even shaped by them. I have 



