Psychology of Animals. 203 



As human psychology became more precise, as careful 

 and critical observations on animal activities increased 

 in number, and as reflex actions began to be The Inclined 

 generally understood, the idea of arranging Plane of 

 vital activities in a series became clearer. 



Beginning at the top, we recognize some rational 

 activities in ourselves, activities which we cannot ex- 

 plain psychologically without postulating general ideas. 

 Whether it be making an engine or guiding an empire, 

 the activity implies certain abstract conceptions, or con- 

 ceptual inferences. 



On a distinctly lower plane are ordinary intelligent 

 actions which demand inferences but not necessarily 

 abstract ideas. To cultivate one's garden cannot be 

 the whole duty of man, as the French philosopher main- 

 tained, for while it demands intelligence it does not 

 necessarily cultivate reason. So far as we know, the 

 animal does not rise above this level of intelligence, or 

 perceptual inference, or concrete judgment. That is to 

 say, the most brilliant illustrations of animal intelligence 

 may be explained psychologically as involving perceptual 

 but not conceptual inference, concrete but not abstract 

 judgment. If we allow the cogency of the logical law 

 of parsimony we must abide by the simplest adequate 

 hypothesis. This is the position of those who allow 

 that animals have intelligence, but maintain that man 

 has a monopoly of reason. But this has no meaning 

 unless a definition of the terms, as above indicated, be 

 agreed upon. 



It is well known, however, that activities originally 

 demanding intelligent control may in the individual life- 

 time become habitual. Being often performed, they 

 bring about, it is supposed, a modification of cerebral 

 structure, the establishment of " habit-tracts ", as some 

 would say; at all events, there is no doubt that they 

 become habitual, whatever that may exactly mean. 



Now, beginning at the lower end of the scale, we 

 recognize in our own life some very simple automatic 

 activities whose psychical side is unknown, such as the 

 physiological rhythms of the heart and lungs, which 

 go on without conscious control, and without external 



