METHODS OF PSYCHOLOGY. 181 



Even if, for example, consciousness and matter in motion were distinct 

 and distinguishable, this would be no argument against a science of 

 physiological psychology. Cerebral and psychical phenomena form one 

 series, and if we have at present no adequate science which concerns 

 itself with this series, it is owing to ignorance of facts, not at all to 

 logical limitations. Matter, time, space and the differential calculus 

 may be as disparate as possible, but are brought together in the science 

 of physics. If the psychologist can not be shut out of the physical 

 world, still less can he be excluded from the sphere of the so-called 

 normative sciences. If any one takes a modern work on ethics or 

 esthetics and tries to separate the treatment of ' what is ' from that 

 of ' what ought to be/ he will find himself engaged in an idle task. 



It appears that the limits of a science are set largely by a psycho- 

 logical constant. A single science has practically the range that can 

 be covered by a single mind or man. From Aristotle to Hobbes and 

 Descartes there were philosophers who could master nearly the whole 

 range of knowledge and advance it in whatever direction they cared to 

 turn. But even in this period as knowledge accumulated, specialization 

 began, and we find astronomers, anatomists and other students of par- 

 ticular sciences. After Galileo and Newton the physico-mathematical 

 sciences became completely divorced from the descriptive natural 

 sciences, while psychology remained under the shelter of philosophy. 

 It was only in the second half of the nineteenth century that the 

 accumulation of certain facts and theories warranted their becoming 

 the chief interest of a psychologist, and even yet it is more usual for a 

 man to pass through a psychological period than to be a permanent 

 psychologist. 



While the first result of increased knowledge has been the estab- 

 lishment of a number of sciences — say a dozen or a score — which have 

 secured proselytes and to a certain extent limited and directed their 

 activities, the further increase of knowledge must break down the arti- 

 ficial limitations. The late emergence of psychology has made easy an 

 elective selection of material. "We not only have psychologists who are 

 also philosophers, but psychologists who are also physiologists, anato- 

 mists, pathologists, zoologists, anthropologists, philologists, sociologists, 

 physicists or mathematicians. Psychology is and will increasingly be- 

 come united with professions and arts, with education, medicine, music, 

 painting and the rest. Even sciences remote from psychology, astron- 

 omy, for example, may have sufficient points of contact to occupy the 

 entire time of a specialist. We not only have combinations between 

 the orthodox sciences, but cross-sections through them, which may to 

 advantage occupy the student, and which have full rights to be ranked 

 as sciences. The phenomena of vision, for example, are scattered 

 among the sciences of psychology, physics, physiology, anatomy, anthro- 



