The Evidence of Mind 35 



7. Inferring Mind from Structure 



Both Yerkes and Lukas urge that the resemblance of an 

 animal's nervous system and sense organs to those of human 

 beings ought to be taken into consideration in deciding 

 whether the animal is conscious or not. Lukas suggests 

 that the criteria of consciousness should be grouped under 

 three heads: morphological, including the structure of 

 the brain and sense-organs, physiological, and teleological. 

 Under the second rubric he maintains that "individual 

 purposiveness " is characteristic of the movements from 

 which consciousness may be inferred ; that individual 

 purposiveness pertains only to voluntary acts, and that 

 voluntary acts and acts " which are preceded by the 

 intention to perform a definite movement, hence by the 

 idea of this movement." We have reached the same con- 

 clusion in the preceding paragraph. The third test of the 

 presence of consciousness, the teleological test, rests on the 

 consideration: "What significance for the organism may 

 be possessed by the production of a conscious effect by 

 certain stimuli?" (445). This test, however, being of a 

 purely a priori character, would seem to be distinctly less 

 valuable than the others. 



Yerkes proposes "the following six criteria in what 

 seems to me in general the order of increasing impor- 

 tance. The functional signs are of greater value as a 

 rule than the structural; and within each of the cate- 

 gories the particular sign is usually of more value than 

 the general. In certain cases, however, it might be main- 

 tained that neural specialization is of greater importance 

 than modifiability. 



I. Structural Criteria. 



i. General form of organism (Organization). 



