The word evolution may be used generally for a development of any kind or more particularly for that form of biological development which was taught by Charles Darwin in his Origin of Species published in 1859. The notion of development was already a familiar one to philosophers and biologists from the time of Aristotle; indeed, nothing could be more obvious than that in the life of an individual animal or plant there is a development from the embryo or seed to the fully grown animal or plant.

The concept of evolution in the Darwinian sense was soon used either literally or figuratively for many other kinds of development than that of plant or animal species. People talked of the evolution of societies, of institutions, of religious, of art, of morals, and of conduct, sometimes merely suggesting that these things change in the course of history, but sometimes with the definite implication that the changes take place in accordance with the principles of natural selection and the survival of the fittest.

If we are engaged in the study of positive science of ethics, and were merely describing man's conduct or even the various standards by which man's conduct has been judged in the course of history, we would certainly need to admit that there has been a development in human conduct and in the standards by which the man is judged.