Christian thinkers did not always construct their notions about the nature of demons on the foundation of pagan thought. In the early third century, a biblical scholar named Origen of Alexandria (ca. 185–ca. 255) wrote a treatise entitled On First Principles, in which he offered the lineaments of a Christian cosmology based on reason and revelation. For Origen, rational souls existed with God since creation, but over time the cooling of their love for their creator caused them to recede from his presence. Some became angels, while others became human beings. Those who receded furthest from God became demons. Origen believed that all souls would eventually return to their creator, but the process of return, which involved a fiery purification after death, could take many lifetimes across multiple worlds. In the end, though, even the Devil would be saved. Origen faced criticism for these speculations during his lifetime and thereafter, which culminated in his condemnation as a heretic in the sixth century. One of his most outspoken critics was Jerome of Stridon (ca. 346–420). Around 410, a Roman Christian named Avitus obtained a Latin translation of On First Principles. Alarmed by what he had read, he wrote to Jerome to ask for an explanation of Origen’s meaning. Jerome’s response was a severe rebuke of the folly of the Alexandrian’s radical cosmology, especially the notion that humans could become demons and vice versa as their souls struggled to migrate back to God.
Take then what you have asked for, but know that there are countless things in this book to be abhorred and that, as the Lord says, you will have to walk among scorpions and serpents…When he comes to deal with rational creatures and to describe their fall into earthly bodies as due to their own negligence…he maintains that after every end a fresh beginning springs forth and an end from each beginning, and that a complete transformation is possible, so that one who is now a human being may in another world become a demon, while one who due to his negligence is now a demon may hereafter be placed in a more material body and thus become a human being. So far does he carry this transforming process that according to his theory an archangel may become the devil and the devil in turn could be changed back into an archangel…moreover, the very demons and rulers of darkness in any world or worlds, if they are willing to turn to better things, may become human beings and so come back to their first beginnings. That is to say, after they have endured the discipline of punishment and torture for a longer or a shorter time in human bodies, they may again reach the angelic heights from which they have fallen. From this, it may be shown that we human beings may change into any other rational being and that not once only but time after time. We and the angels will become demons if we neglect our duty, and demons may attain to the ranks of angels, if they cultivate sufficient virtue…In the second book he maintains a plurality of worlds; not, however, as Epicurus taught, many similar worlds existing at the same time, but a new one beginning each time that the old comes to an end.[2] There was a world before this world of ours, and after it there will be first one and then another and so on in regular succession. He is in doubt whether one world shall be so completely similar to another as to leave no room for any difference between them or whether one world shall never wholly be indistinguishable from another…For he evidently maintains that all bodies will perish and that we will be incorporeal, as according to him we were before we received our present bodies. Again, he argues for a variety of worlds and maintains that angels will become demons, demons either angels or men, and men in their turn demons; in a word, everything will be turned into something else…And after a lengthy discussion, he argues that all corporeal creatures must exchange their material form for subtle and spiritual bodies and that all substance must become one pure and inconceivably bright body, of which the human mind can at present form no conception.