Whatever forces may govern human life, if they are to be recognised by man, must betray themselves in human experience. Progress in science or religion, no less than in morals and art, is a dramatic episode in man’s career, a welcome variation in his habit and state of mind; although this variation may often regard or propitiate things external, adjustment to which may be important for his welfare. The importance of these external things, as well as their existence, he can establish only by the function and utility which a recognition of them may have in his life.