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 sensation would 

 seem to be immaterial to the performance of the movement. 

 These unconscious reactions in human beings are character- 

 ized 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 un- 

 conscious and to .become uniform. 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 response of 

 microscopic animals to stimulation, better facilities for ob- 

 servation 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 presence 

 of mind. Is mere variability in behavior, mere irregularity 

 in response, to be taken as such a test ? Not if we argue from 

 our own experience. While that portion of our own be- 

 havior which involves consciousness shows more irregularity 



