Page:Popular Science Monthly Volume 40.djvu/525

Rh, and has its foundation, deepened by every increase of knowledge."

Definiteness has been given to the question of the nature of animal intelligence by the new doctrine of evolution. If man is descended from some lower organic form, we ought to be able to make out not merely a physical but a psychical kinship between him and the lower creation; and the more favorable estimate of the animal mind taken by the modern savant is of great assistance here. Mr. Darwin has, indeed, shown in his valuable contributions to the subject, that the rude germ of all the more characteristic features of the human mind may be discovered in animals. At the same time, Mr. Darwin's investigations in this direction amounted only to a beginning. The crux of the evolutionist, the tracing of the continuity of crude, formless animal inference, up to the highest structural developments of logical or conceptual thought, still remained. And so, the most powerful attack on the theory of man's descent has come from the philosopher, the logician, and the metaphysical philologist, who have combined to urge the old argument that conceptual thought indissolubly bound up with language sets an impassable barrier between man and brute.

Mr. Darwin's unfinished work has now been taken up by one who adds to the biological knowledge of the expert a considerable acquaintance with psychology. In his previous volume, Mental Evolution in Animals, Dr. Romanes took a careful psychological survey of the animal world for the purpose of tracing out the successive grades of its mental life. In his recent volume. Mental Evolution in Man (Origin of Human Faculty), he essays to trace forward this general movement of mental evolution to the point where logical reasoning or "conceptual thought" may be distinctly seen to emerge. That is to say, he adroitly seeks to leap the "impassable" barrier by merely denying its existence. Human reasoning and animal inference are not two widely dissimilar modes of intellection. The one is merely a more complex expansion of the other. If you start either at the human or the animal bank you can pass to the opposite one by a series of steppingstones. In other words, the higher human product can be seen to have been evolved out of the lower by a continuous process of growth.

Dr. Romanes's present contribution to the theory of evolution is thus emphatically the construction of hypothetical steppingstones for the purpose of passing smoothly from the territory of animal to that of human reasoning. In order to this, he has on the one hand to follow up animal intellection to its most