METHODS OF PSYCHOLOGY. 183 



goes to the ends of the earth and photographs a solar eclipse, making 

 all sorts of measurements and calculations, we may say that this is an 

 observation and not an experiment, but we have not made a useful 

 definition; neither do we gain anything by deciding whether it is an 

 experiment when a baby pulls apart a doll to see what is inside. The 

 real distinction is between the casual experimenting and observing of 

 daily life, and the planned and purposive experiment and observation 

 of science. Science is experimental qua science. 



I consequently object to making experimental psychology a branch 

 of psychology. It is a method in psychology, which is extended just 

 as rapidly as psychology becomes a science. The purely introspective 

 or analytic observer does, according to the current definition/ con- 

 tinually make experiments, because his introspection itself alters the 

 process that he is observing, thus sometimes making his observations 

 invalid as a description of natural conditions. On the other hand, the 

 student in the laboratory may measure the process without any intro- 

 spection or interference with it, and this may not be technically an ex- 

 periment at all, but it gives a scientific description of the normal 

 course of mental life. We are told that Adam gave a very appropriate 

 name to the hog ; science is not always so fortunate in its nomenclature. 



Most experiments, letting experiments mean attempts to increase 

 scientific knowledge, are also measurements. Measurement is only a 

 description; but it has proved itself to be the most economical, wide- 

 reaching and useful form of description. What language was for the 

 evolution of primitive man, measurement is for the advance of mod- 

 ern science. As a word selects similarities and ignores differences, so 

 a measurement selects certain similarities from the concrete manifold- 

 ness of things. That such a great part of the world can be described 

 in terms of a few units of measurement, and that this description 

 should lead to such useful applications, is truly marvelous and admir- 

 able. As I am writing these paragraphs, I have received a manuscript 

 in which the author explains that the fact that the earth rotates on its 

 axis in twenty-four hours, not varying a second from day to day, is a 

 conclusive proof that it was created and set rotating by a benevolent 

 being. If the days were shorter, he says, we could not get our work 

 done, and if the days were longer, we should be too tired by night. It 

 almost seems as though the world were made in such comparatively 

 rational fashion in order that we may measure it. 



The physicist counts, and he measures time, space and energy. He 

 has intractable matter with its seven and seventy elements, and he may 

 come across a substance as complex and perplexing as radium. But 

 by and large he can describe his world in certain quantitative formu- 

 las. It is true that he accomplishes this in part by unloading on psy- 

 chology qualitative differences, such as colors and tones. So much the 



