In the previous chapters I have been dealing with the relations between medicine, magic, and religion descriptively, and from the sociological and psychological points of view. I showed that, in Melanesia and New Guinea, which I chose as the region to illustrate my subject, there is an intimate connexion between three sets of social process, which are clearly distinguished from one another by ourselves and other civilized peoples. I dealt briefly with some of the psychological factors underlying the union between three kinds of process, but left altogether on one side any consideration of the mechanisms by which the relations between medicine, magic, and religion had come into being, and those by which processes so closely related in one part of the world had elsewhere become distinct and self-contained departments of social life. I have chosen this historical and evolutionary treatment for the second half of this book.