The theory of natural selection as applied to the ordinary spheres of plant and animal life, may perhaps, for some purposes, neglect consideration of the fact that it presupposes a tendency to variation in the organisms whose growth it describes. But, when the variation in the behaviour of the organism becomes conscious and designed, there is thereby produced a preliminary indication or determination of the lines on which natural selection is to work. And, before the theory of evolution can give a full account of the ethical in man, it must distinguish consciously-determined from merely natural action, and give an analysis of what is implied in the former. We must bear in mind that it may be the case that the ground and possibility of progress and of the efficiency of ideal ends in human conduct--which "adaptation to environment" has been unable logically to explain or leave room for--are to be found in this differentiating fact of conscious activity. But we must first of all see whether, from the empirical characteristics of variation, we can extract an ethical end or any guide for conduct. * * * * * [Sidenote: 2. End suggested by this tendency to variation] [Sidenote: (_a_) prescribes self-development rather than self-preservation,] 2. "The lower animals," says a writer on biology, "are just as well organised for the purposes of their life as the higher are for theirs. The tape-worm is relatively quite as perfect as the man, and distinguished from him by many superior capabilities."[227] It is incorrect to look upon the evolution of animal life as working upon one line, so that the different kinds of living beings can be arranged, as it were, in an order of merit, in which the organisation of the higher animal plainly excels that of the lower. The conditions of life are manifold and various enough to permit of the existence of many species equally perfect in relation to their environments. The fact that we are still able to speak of one species or one animal as higher than another, is not owing to the one being better adapted to its environment than the other, but is supposed rather to be due to the higher forms having "their organs more distinctly specialised for different functions."[228] Even Mr Spencer, for whom equilibrium is the goal of life, implicitly admits that "adaptation" alone is not the end of human action, by his doctrine that the degree of evolution may be measured by the complexity of the adjustments it effects between organism and environment. The end, therefore, it may be said, is no longer the mere "self-preservation" found in adaptation to environment, but the "self-development" which implies temporary disharmony between organism and surroundings.