1 64 THE SCIENCE OF LOGIC 



239. EXPERIMENT : ITS RELATIONS TO OBSERVATION. 

 Experiment is simply observation under special conditions brought 

 about by the observer himself, and modifying the object observed, ^^he 

 qualification introduced in the latter phrase is essential ; for if 

 the special conditions mentioned modify only the observer s 

 point of view, or his power or medium of observation, leaving the 

 object unchanged,, we do not speak of such an observation as an 

 experiment. Thus, &quot;vivisection is experiment because the deter 

 minate conditions it produces enter as factors into the action of 

 the organism observed &quot; ; while &quot; common dissection is not ex 

 periment, though it introduces conditions in the way of separation 

 and demarcation as definite as anything can be,&quot; 1 because these 

 conditions merely prepare, without changing or forming part of, 

 the object under observation. So, also, we speak of observations 

 with the microscope, telescope, etc. The transition from pure 

 observation to definite experiment is, however, gradual ; they 

 differ in degree, not in kind. This is best illustrated in what have 

 been curiously called nature s experiments, or natural experiments. 

 In these the phenomena observed are altogether beyond our con 

 trol and, therefore, cannot be influenced by any activity of ours ; 

 but we take advantage of specially favourable circumstances, or 

 select a specially favourable medium or point of view, for our 

 observations : as when, for example, astronomers select special 

 times and places for their observations ; or meteorologists climb 

 high mountains, or ascend in balloons, to make climatic observa 

 tions ; or scientists lay long lines of wire, or erect magnetic stations, 

 or construct seismographs, for the purpose of observing and re 

 cording electric, magnetic, or seismic disturbances. 



Experiment may, therefore, be rightly regarded as a special 

 kind or mode of observation : the latter being the genus, the 

 former a species. There is no real opposition between them, 

 although in observation the natural and passive aspects, in experi 

 ment the artificial and active aspects, predominate. The superior 

 value of the latter, as compared with the former, arises from the 

 fact that the common object of both the acquiring of a full and 

 exact knowledge of all the operative conditions influencing the 

 phenomenon under investigation can be attained only by calling 

 in the aid of experiment, and not by simple observation alone. 

 This will appear presently from an examination of the proper 



^OSANQUET, Logic, vol. ii., p. 145. 



