The _Letter to Anebo_ inquires concerning the nature of the gods, the demons, and the stars; asks for an explanation of divination and astrology, of the power of names and incantations; and questions the employment of invocations and sacrifice. Other topics brought up are the rule of spirits over the world of nature, partitioned out among them for this purpose; the divine inspiration or demoniacal possession of human beings; and the occult sympathy between different things in the material universe. In especial the art of theurgy, a word said to be used now for the first time by Porphyry,[1367] is discussed. It may be roughly defined for the moment as a sort of pious necromancy or magical cult of the gods. Porphyry raises various objections to the procedure and logic of the theurgists, diviners, enchanters, and astrologers, which Iamblichus, as we shall henceforth call the author of the _De mysteriis_ as a matter of convenience if not of certainty, endeavors to answer, and to justify the art of theurgy. [Sidenote: Questions concerning divine natures.] We may first note the theory of demons which is elicited from Iamblichus in response to Porphyry’s trenchant and searching questions. The latter, declaring that ignorance and disingenuousness concerning divine natures are no less reprehensible than impiety and impurity, demands a scientific discussion of the gods as a holy and beneficial act. He asks why, if the divine power is infinite, indivisible, and incomprehensible, different places and different parts of the body are allotted to different gods. Why, if the gods are pure intellects, they are represented as having passions, are worshiped with phallic ritual, and are tempted with invocations and sacred offerings? Why boastful speech and fantastic action are taken as indications of the divine presence; and why, if the gods dwell in the heavens, theurgists invoke only terrestrial and subterranean deities? How superior beings can be invoked with commands by their inferiors, why the Sun and Moon are threatened, why the man must be just and chaste who invokes spirits in order to secure unjust ends or gratify lust, and why the worshiper must abstain from animal food and not touch a corpse when sacrifices to the gods consist of the bodies of dead victims? Porphyry wishes further an explanation of the various _genera_ of gods, visible and invisible, corporeal and incorporeal, beneficent and malicious, aquatic and aerial. He wants to know whether the stars are not gods, how gods differ from demons, and what the distinction is between souls and heroes. [Sidenote: Orders of spiritual beings.]