With the progress of civilisation an organised body of sorcerers necessarily grows up. But an organised body of sorcerers also implies an organised body of spirits, and an organised system of controlling them. The spells and charms which have been handed down from the past are formed into a system, and the spirits themselves are classified and defined, while special functions are assigned to them. The old unorganised animism passes into an organised shamanism, such as still prevails among certain Siberian tribes. The sorcerer is on the high road to becoming a priest. Between the sorcerer and the priest, however, there is a gulf too wide to be spanned. The religious conceptions presupposed by them differ in kind as well as in degree. The nature of the superhuman beings by whom man is surrounded, and the relations which he bears to them, are essentially different in the two cases. The priest may also be a sorcerer, but the sorcerer cannot be a priest. Can shamanism develop naturally into theism, and the sorcerer into the priest? Or is there need of foreign influences and of contact with other ideas and religious beliefs? I should myself be inclined to adopt the second alternative. Theism may absorb shamanism, and the priest throw the ægis of his authority over the sorcerer, but the natural development of the one into the other is contrary to the facts of psychology as well as to those of history. The evolution of a god out of the shaman’s ghost may be conceivable, but no evidence for it exists. The superstitions and beliefs of shamanism linger, indeed, under a theistic religion, and the polytheism of Babylonia was no exception to the rule. Up to the last the magician flourished there, and the spells he worked were recognised by the religion of the State. But for all that they stood outside the religion of the State, harmonising with it just as little as the superstitions of popular folk-lore harmonise with the religion we profess. No one would assert that the Christianity of to-day has grown out of beliefs like that in the vampire which still holds such sway in some of the Christian countries of Europe; and there is just as little reason for asserting that the vampire of the primitive Sumerian developed into a Babylonian deity. They represent two diverse currents of belief, which may for a time run side by side, but never actually coalesce.