Men have to learn to find their happiness not in what saps health or invites death, but in what makes for health and life. What definition of morality emerges from this? The foregoing summary permits us to formulate a definition of morality. Historically, there has been a gradual, though not continuous, progress toward CODES OF CONDUCT WHICH MAKE FOR THE PRESERVATION OF LIFE AND FOR HAPPINESS. These codes have received an imaginative consecration, and all sorts of secondary sanctions; but it is their underlying utility that is of ultimate importance. Very simple and obvious causes have continually tended to destroy customs which made in the contrary direction and to select those which, however originating, made for either or both of these two ends. It is these customs, important for the welfare of the individual or tribe, which we call morality. If the original instincts of mankind had been delicately enough adjusted to their needs, there would have been no need of these secondary and overruling impulses, and the differentiation of impulse and duty, of the natural and the spiritual man, would never have arisen. But actually, mankind inherited from its brute ancestry instincts which, unguided, wrought great harm. Without the development of some system of checks men would forever have been the prey of overindulgence, sexual wantonness, civil strife, and apathy. They would have remained beasts and never won their dominance on the earth. Even rudimentary moral codes came as an amelioration of this dangerous and unhappy situation; they enabled men, by abstention from dangerous passions and from idleness, to make their lives efficient, interesting, and comparatively free from pain; by cooperation and mutual service to resist their enemies and develop a civilization. Morality thus has been the greatest instrument of progress, the most fundamental of man's achievements, the most important part of the wisdom of the race. Is moral progress certain?