i8 2 POPULAR SCIENCE MONTHLY. 



pology, zoology, embryology, pathology, chemistry, mathematics, etc.; 

 they are important factors in certain fine and industrial arts; they 

 are the basis of one of the most important medical disciplines. 

 Why should not a man be a ' visionologist ' or ' sightonomer ' ? 

 When President Hall gives us an original and unique book on adoles- 

 cence, nothing is gained by attempting to assign it to one of the con- 

 ventional sciences. The work of Dr. Galton appears to me to be par- 

 ticularly unified, but it does not belong to psychology, nor to any other 

 science. Why not call him an opportunist, or a liberal unionist, or a 

 Galtonist, or better still call him no name at all? 



In objecting to an artificial limitation of the field of the psychol- 

 ogist, I by no means want to aggrandize his office or to let psychology 

 eat up the other sciences. The student of psychology is limited by the 

 capacity of the human mind and of his own particular mind; he can, 

 on the average, cover a range about as large as that of the student of 

 any other science. If he would gladly get, he would also gladly give. 

 If he is an imperialist who would set his flag on every corner of the 

 earth, he yet tears down no other flag and welcomes the invasion of his 

 own territory by every science. 



As I claim for psychology the freedom of the universe in its sub- 

 ject-matter, so I believe that every method of science can be used by 

 the psychologist. The two great achievements of science have been 

 the elaboration of the quantitative method on the one hand and of the 

 genetic method on the other. The uniformity of nature and the ration- 

 ality of things are here presented in their most convincing, or at all 

 events most plausible form. It would be an irreparable limitation if 

 either of these methods did not apply in psychology. In my opinion 

 they not only do obtain but must obtain. The mental and the physical 

 are so inextricably interfused that quantitative and genetic uniformities 

 could not exist in the physical world if absent from consciousness. If 

 our mental processes did not vary in number, if they did not have time, 

 intensity and space relations, we should never have come to apply these 

 categories in physics, chemistry or astronomy. I am not prepared to 

 attempt to clear up the logical questions involved ; when water is muddy 

 it is often wise to wait for it to settle rather than to keep stirring it up. 



Under the conditions of modern science nearly all observations are 

 experiments and nearly all experiments are measurements. A sharp 

 distinction is usually drawn between an experiment and an observation. 

 Thus Wundt, following Mill and other logicians, defines an experiment 

 as an observation connected with an intentional interference on the 

 part of the observer in the rise and course of the phenomena observed. 

 But it is as properly an experiment to alter the conditions of observation 

 as to alter the course of the phenomena observed. If the astronomer 



