Makch 12, 1915] 



SCIENCE 



379 



all. It is always possible to determine the 

 laws of any mental operation, as has been 

 done by the experiments on memory, by 

 the statistical method applied to everything 

 from heredity to advertising by the Cattell 

 school and others, by the investigators in 

 education, in medicine, in the studies in 

 eiBcieney, and also in the early experiments 

 on Weber's law and reaction times. 

 Whether classed as conscious processes or 

 as behavior, every one is capable of de- 

 ciding whether a sound is more intense 

 than the preceding, whether a picture is 

 more or less beautiful than another, of re- 

 calling and recording the words that were 

 spoken in a conversation a month ago 

 (whether truly or not is for the experi- 

 menter to decide) of pressing a key when 

 a stimulus is given. That is all that these 

 experiments require. How these processes 

 are carried out is entirely indifferent. 

 Granting that they may be carried out, a 

 science of psychology is possible. All dis- 

 agreement between schools is as to how 

 these judgments are made, that they are 

 made all agree. 



This conclusion does not mean that psy- 

 chology need stop here. How one remem- 

 bers, the mental antecedents of an act and 

 all questions of classification and of ulti- 

 mate explanation are bound to be raised 

 and are at once valuable and interesting — 

 my only contention is that the nature of 

 the explanation offered makes no difference 

 to the fact to be explained, a statement 

 that is obvious enough but which seems to 

 be lost sight of in much of the controversy 

 that is raging. The laws that I have been 

 mentioning correspond to the simple phys- 

 ical laws of the lever, of gravitation, Ohm's 

 law and Joule's law, etc., while the con- 

 troversy rages about questions related to 

 the physicist's discussion of the nature of 

 ether and the atom and the so-called law of 

 relativity. Whether one is to use intro- 



spection or observation as the method of 

 psychology arises only when one seeks an 

 explanation of mental laws, not while dis- 

 covering them. For this explanation intro- 

 spection, observation and speculation on 

 the basis of both and of knowledge obtained 

 from all related fields can, I believe, all be 

 used to advantage. No one method is com- 

 plete in itself; in most experiments all 

 three are used, no matter to what school 

 the investigator belongs. 



One may take as an instance such an 

 experiment as those of Ach on action with 

 the reaction time method. The funda- 

 mental result, let us say, is to determine that 

 the response that follows, showing two num- 

 bers written one over the other, depends 

 for its character and the time required 

 upon the purpose. That fact is independ- 

 ent of the method used. If one is inter- 

 ested in the antecedents of the movement 

 in consciousness, one must introspect. But 

 raw products of introspection are value- 

 less. One must be assured that the images 

 are essential by repetition of the intro- 

 spection with the same individual and other 

 individuals under varying conditions. To 

 determine the nature of the purpose and 

 the way it acts one may see if it has any 

 conscious form, and may indulge in phys- 

 iological speculations, may look for anal- 

 ogies in physiological laws, or one may ob- 

 serve the bodily attitude, the set of the 

 muscles before and during the response. 

 The final acceptance of any explanation 

 will be found to depend upon a harmony 

 of all these observations with each other 

 and with related facts. In any case, the 

 determination of the laws is related to 

 their explanation as observed fact is re- 

 lated to theory in physics or physiology. 



The question might well be raised 

 whether the certainty of recognition, of de- 

 cision and the other processes we have men- 

 tioned as constituting the primary facts of 



