The Evidence of Mind 29 



some ground for holding that the reactions of the lowest 

 animals are unconscious. This ground consists in the ap- 

 parent lack of variability which characterizes such reactions. 

 In our own case, we know that certain bodily movements, 

 those of digestion and circulation, for example, are normally 

 carried on without accompanying consciousness, and that in 

 other cases where there is consciousness of the stimulus, as 

 in the reflex knee-jerk, it occurs after the movement is 

 initiated, so that the nervous process underlying the sensa- 

 tion would seem to be immaterial to the performance of 

 the movement. These unconscious reactions in human 

 beings are characterized by their relative uniformity, by 

 the absence of variation in their performance. Moreover, 

 when an action originally accompanied by consciousness is 

 often repeated, it tends, by what is apparently one and the 

 same process, to become unconscious and to become uni- 

 form. There is consequently reason for believing that when 

 the behavior of lower animals displays perfect uniformity, 

 consciousness is not present. On the other hand, an 

 important reservation must be made in the use of this 

 negative test. It is by no means easy to be sure that an 

 animal's reactions are uniform. The more carefully the 

 complexer ones are studied, the more are variability and 

 difference brought to light where superficial observation 

 had revealed a mechanical and automatic regularity. It is 

 quite possible that even in the simple, apparently fixed re- 

 sponse of microscopic animals to stimulation, better facili- 

 ties for observation might show variations that do not now 

 appear. 



This matter of uniformity versus variability suggests a 

 further step in our search for a satisfactory test of the pres- 

 ence of mind. Is mere variability in behavior, mere 

 irregularity in response, to be taken as such a test ? Not if 



