1 84 POPULAR SCIENCE MONTHLY. 



more satisfaction to us if we can reduce them to quantitative order. 

 Perhaps we shall have only partial success; but it may fairly be urged 

 that psychology has done as much in this direction in fifty years as 

 physics accomplished to the time of Galileo or chemistry to the time 

 of Lavoisier. 



The psychologist counts and he measures time, space and intensity. 

 Even if it were true — I think it is not true — that mental magnitudes 

 are not measurable, it would none the less be the case that mental 

 processes are described in quantitative terms. This is attempted and 

 accomplished in most of the researches published in our psychological 

 journals. They describe measurements and the correlation of quan- 

 tities; they show that a mental mechanics is more than a possibility. 



The physical sciences have been primarily quantitative and the bio- 

 logical sciences are primarily genetic, but the physical sciences must 

 become genetic and the biological sciences must become quantitative. 

 Psychology is from the start both quantitative and genetic. It may 

 indeed be claimed that it is the science in which the genetic method 

 has the most complete application. Every mental state and every form 

 of activity is the result of development from previous conditions. If 

 explanation, as distinguished from description, is possible anywhere in 

 science it is possible here. It is certainly difficult to penetrate by 

 analogy into the consciousness of the lower animals, of savages and of 

 children, but the study of their behavior has already yielded much and 

 promises much more. Although those who make their psychology co- 

 terminous with introspection can not enter far into this field, they 

 still have their own genetic problems. In whatever direction we turn 

 the harvest is waiting; it is only the reapers who are few. Almost 

 every observation, experiment or theory of organic evolution offers 

 parallel problems for the psychologist. The development of the indi- 

 vidual opens questions more numerous and more important for psy- 

 chology than does the development of the body for other sciences. 

 Senile, degenerative and pathological conditions are all there for psy- 

 chological investigation. The evolution of society and the inter-rela- 

 tions of individuals are being gradually brought within the range of 

 genetic psychology. It is quite possible that the chief scientific prog- 

 ress of the next fifty years will be in this direction. 



The problems of psychology are certainly made endlessly complex 

 by the fact that we have to do not with the development and condition 

 of a single mind or individual, but with innumerable individuals. 

 The traditional psychology has been disposed to ignore individual dif- 

 ferences; but in attempting to prescribe conditions for all minds, it 

 becomes schematic and somewhat barren. It is surely wasteful to 

 select those uniformities that are true for all and to throw away those 

 differences which are equally fit material for scientific treatment. 



