Page:Mind (Old Series) Volume 12.djvu/59

 46 J. WAED : the model was physics. Since Kant's day the science of physics has made great strides ; and a new science, biology, has come into being : from both at least in respect of method the psychologist has much to learn. To be more specific we have first the modern doctrine of energy with the theory of dimensions, and we have next that hypothesis which has entirely transformed our conceptions concerning organised life, the hypothesis of evolution. Also we may say generally that the problem of psychology is twofold : (1) to analyse the facts of mental life, and (2) to ascertain the course and conditions of mental development. It is especially in dealing with the second problem that the biologist inspires us to attempt a wider range and to take a larger view. We see him refer all the varied types of life to a few simple forms ; the differentiation of organs, in the highest and lowest alike, to changes in two or three primi- tive germinal layers ; while their several physiological functions are traced back to the fundamental properties of protoplasm, such as contractility, irritability, &c. Now what seems desirable in psychology is an equally general- ised analysis of the broad facts we include under the term a mind 'a mind/ and not the stuff or substance which dualistic philosophers oppose to that other stuff they call matter. But in trying to take a hint from the biologist we come at once upon a difficulty. He can see his simplest creature, the amoeba, manifest the several vital functions ; he can see the impregnated ovum segment, differentiate its primitive layers and develop stage by stage ; he can range the leading types of the animal or vegetable kingdom in their appropriate order before his eyes. The psychologist can do nothing at all of this kind directly, and only very little indirectly. He cannot analyse the simplest forms or stages of consciousness and note the progressive advance from these to higher. He is sure beyond all serious doubt that mind and nervous organisation are concomitant, much, for example, as colour and wave-length are. But still a given nervous development is scarcely more a clue to the mind that corresponds than the wave-length of violet, as compared with that of red, is a clue to the difference of sensation that accompanies retinal excitation by these waves. As far as direct acquaintance goes the psychologist is confined to the most complex form of mind, and that in its maturity. His observation of himself, supplemented by like observations on the part of others, have made possible a certain objective knowledge of the human mind, which, broadly speaking, is as plain and as verifiable as other depart-