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THE POPULAR SCIENCE MONTHLY. 



The methods of psychology are the same as those of other 

 sciences. Science has its beginnings in common knowledge of 

 daily life collected for practical ends. This knowledge is sys- 

 tematized, often in an artificial manner, and facts, often fancies, 

 more remote from daily experience and usefulness are added. 

 Attempts are made to simplify and explain, usually by arbitrary 

 hypotheses. Thus it was thought by the early Greek physicists 

 that the earth is explained by saying that it all consists of water 

 or air or fire. Even in recent times it was thought an explana- 

 tion to say that water rises in the pump because Nature abhors a 

 vacuum, or that life is explained by the presence of a vital fluid. 

 But as science advances it depends more and more on experiment 

 and measurement. Data are seldom admitted which can not be 

 verified by any competent observer, and mere matters of fact take 

 a subordinate place. Exact science consists almost exclusively of 

 measurements and the relations of quantities. 



Psychology until very recently was in the position of science 

 before experiment and measurement had been used. It consisted 

 largely of useless descriptions, artificial classifications, and verbal 

 explanations. A preference was given to matters which are ex- 

 traordinary and unverifiable. But in the progress of science it 

 has at last become possible to apply experiment and measurement 

 to the mind. We have to-day laboratories of psychology where 

 facts may be discovered, measurements made, and the results veri- 

 fied by every trained student. 



To prevent misunderstanding, it may be worth while to notice 

 what is not done in laboratories of psychology. They are not in- 

 tended for the study of physiology. The functions of the nervous 

 system may throw light on the workings of the mind, but the 

 debt is reciprocal. We know, indeed, more concerning attention, 

 memory, and thought than concerning the cerebral processes 

 which may precede or accompany them. The commonly used 

 term physiological psychology is awkward. There is a science of 

 physiology and a science of psychology, and there are relations 

 between body and mind. But these relations are wider than this 

 — they are between matter and mind. Thus we know that vibra- 

 tions of a special sort may be accompanied by a sensation which 

 we call blue, but we know almost nothing concerning the corre- 

 sponding processes in the eye and brain. The world is one world, 

 and all science is interdependent, but the development of psychol- 

 ogy has drawn a sharper line between mental and physical 

 processes than was ever recognized before. The distinctions of 

 material science are comparatively artificial, resting on our igno- 

 rance rather than on our knowledge. Whether bodies be as large 

 as planets or as small as atoms is not a matter of great conse- 

 quence. If we but knew the laws of matter in motion, they would 



