Here, then, we have to enter on the consideration of moral phenomena as phenomena of evolution; being forced to do this by finding that they form a part of the aggregate of phenomena which evolution has wrought out. If the entire visible universe has been evolved—if the solar system as a whole, the earth as a part of it, the life in general which the earth bears, as well as that of each individual organism—if the mental phenomena displayed by all creatures, up to the highest, in common with the phenomena presented by aggregates of these highest—if one and all conform to the laws of evolution; then the necessary implication is that those phenomena of conduct in these highest creatures with which Morality is concerned, also conform. (§23 ¶1)

The preceding volumes have prepared the way for dealing with morals as thus conceived. Utilizing the conclusions they contain, let us now observe what data are furnished by these. We will take in succession—the physical view, the biological view, the psychological view, and the sociological view. (§23 ¶2)