Let us begin with the technical side--the change in psychology. We are only just now commencing to appreciate how completely exploded is the psychology that dominated philosophy throughout the eighteenth and nineteenth centuries. According to this theory, mental life originated in sensations which are separately and passively received, and which are formed, through laws of retention and association, into a mosaic of images, perceptions, and conceptions. The senses were regarded as gateways or avenues of knowledge. Except in combining atomic sensations, the mind was wholly passive and acquiescent in knowing. Volition, action, emotion, and desire follow in the wake of sensations and images. The intellectual or cognitive factor comes first and emotional and volitional life is only a consequent conjunction of ideas with sensations of pleasure and pain. The effect of the development of biology has been to reverse the picture. Wherever there is life, there is behavior, activity. In order that life may persist, this activity has to be both continuous and adapted to the environment. This adaptive adjustment, moreover, is not wholly passive; is not a mere matter of the moulding of the organism by the environment. Even a clam acts upon the environment and modifies it to some extent. It selects materials for food and for the shell that protects it. It does something to the environment as well as has something done to itself. There is no such thing in a living creature as mere conformity to conditions, though parasitic forms may approach this limit. In the interests of the maintenance of life there is transformation of some elements in the surrounding medium. The higher the form of life, the more important is the active reconstruction of the medium. This increased control may be illustrated by the contrast of savage with civilized man. Suppose the two are living in a wilderness. With the savage there is the maximum of accommodation to given conditions; the minimum of what we may call hitting back. The savage takes things "as they are," and by using caves and roots and occasional pools leads a meagre and precarious existence. The civilized man goes to distant mountains and dams streams. He builds reservoirs, digs channels, and conducts the waters to what had been a desert. He searches the world to find plants and animals that will thrive. He takes native plants and by selection and cross-fertilization improves them. He introduces machinery to till the soil and care for the harvest. By such means he may succeed in making the wilderness blossom like the rose.