Medicine, magic, and religion are abstract-terms, each of which connotes a large group of social processes, processes by means of which mankind has come to regulate his behaviour towards the world around him. Among ourselves these three groups of process are more or less sharply marked off from one another. One has gone altogether into the background of our social life, while the other two form distinct social categories widely different from one another, and having few elements in common. If we survey mankind widely this distinction and separation do not exist. There are many peoples among whom the three sets of social process are so closely inter-related that the disentanglement of each from the rest is difficult or impossible; while there are yet other peoples among whom the social processes to which we give the name of Medicine can hardly be said to exist, so closely is man’s attitude towards disease identical with that which he adopts towards other classes of natural phenomena.