If, in animal psychology, we are to use the words pleasure and pain (as the antithesis of pleasure)--and they seem more properly to belong to a plane of mental development to which animals probably have not attained--we may say that the pleasure or the pain which attaches to any centre of interest in the situation is that which gives it attractive or repellent meaning; it furthers conation either towards or, as Hobbes would say, fromwards. But if we put the matter in this somewhat abstract form, let us keep in view, if it be only in the background of our thought, the kind of concrete example which may be adduced in its illustration--the dog with his attractive bone, the kitten that has raced off at sight of him, the cock-sparrow with trailing wings hopping after his mate, the falcon stooping on her quarry, the rabbit diving into his burrow at sight of the fox, and so forth. If we have such cases in view, where the centre of the situation has acquired or is acquiring meaning, a meaning which in large degree attaches to the external nucleus of the situation with only the germs of subjective reference, we may, perhaps, summarize the position by saying that in each case some pleasure to be gained or some pain to be avoided is the psychological end of conation.
But in each case the conation has also a biological end--the preservation and conservation of the race. “An animal,” said Darwin,[181] “may be led to pursue that course which is most beneficial to the species by suffering, such as pain, hunger, thirst, or fear; or by pleasure, as in eating and drinking, and in the propagation of the species; or by both combined, as in the search for food.” The important point here to notice is that the two ends agree--the psychological end of the attainment of pleasure and the avoidance of pain, and the biological end of race preservation. Under the joint influence of pleasure and pain, the needle of animal life sets towards the pole of beneficial action.
This consonance of end was in old days ascribed to the beneficent foresight of the Creator. The modern view, that it is a product of evolution, does not necessarily ascribe it to any other ultimate cause. For many still piously hold that evolution is only a name which we give to the method of creation. And there is not a fact or generalization in science by which such a conclusion can be disproved, for the premises lie outside the field of scientific inquiry. But the consonance of end is, for science, a remarkable fact, and one worthy of attentive consideration.