As Mr. Spencer points out, the acceptance of this law implies not merely an entire harmony between the existence of an organism and its environment, but it also implies various degrees of life. The greater the number and variety of correspondences established between an organism and the immensities of the external world--immensities displayed not only in the multiplicities of individual objects, but also in the grandeur of their collective interrelations--the greater the degree of life. Much stress is laid by Mr. Spencer upon this Quantitative character of Life. Much more, indeed, than upon mere continuity, although the latter is to a certain extent essential to the former. Subordinate to this notion, advance in degree of life is found to proceed from a simple, incoherent, and indefinite life to a more and more definite, coherent and complex set of relations with the environment. But side by side with this development, and indeed in a manner to be likened to that of a geometrical progression, the subjective factor has advanced in relative importance. In its more rudimentary development, Mr. Spencer finds pain to be the concomitant of those states of the physical organism which tend to its destruction, and pleasure to be the concomitant of those states which tend to its promotion. Thus hunger is a pain indicative of the absence of those supplies of energy to be obtained from the environment, which are requisite for the continuance of the organism's activity, while the pleasure of feeding is concomitant with the due supply of the energy necessary for the continuance of organic function. Pleasure and pain, therefore, become motives, and the attainment of the one and the avoidance of the other work together for the continuance of life. Pleasures and pains are relative to the organism--according to the physiological constitution and structure of the organism so are its pleasures and its pains. The concomitant of some of the structures and functions of the organism has been not merely sentiency but perception. Mind has developed from the distinguishment, identification, and recognition of modes of sentiency. These functions and structures have been accompanied by pleasure and pain, and have formed the basis of the pleasures of intellectual activity in their multiform variety. From their very nature in relation to the environment they have increased wonderfully the quantitative development of life. With the increase of mind has proceeded the recognition of the part played in the organic universe by feeling. This recognition of the existence of feeling--of the susceptibilities of external organisms to pleasure and pain--has formed the basis of a large part of the adaptations of organisms in relation to their organic environment. Adaptations revealing this recognition are to be seen not only more manifestly in the actions of man and the animals, but also in the functions of plants, strange as this may seem.