Of course the story is far richer than the few Biblical verses that are believed to refer to it and much embellishment has been added over the centuries from apocryphal, not to say heterodox, sources and literature such as Dante’s Inferno.

One need not be a devout Christian to be familiar with this story, it is a part of popular culture as familiar to Americans as the Civil War or the assassination of President Kennedy. Considering this, however, one is struck by the amount of presumption that such a concept rests upon. And yet this background surely is widely known, at least to some degree, as it is the background of popular films, novels and art. When watching a film such as The Exorcist, simply think about the fact that the filmmaker never explains the cosmology that underlies the film; he does not have, the audience already knows it. Many, probably a majority, would agree that, while the movie is clearly fictional and takes artistic license with its subject, the basic worldview is in accord with their own personal beliefs.

This state of affairs, it hardly needs to be pointed out, is just the contemporary (albeit popular) perspective on the subject. Even if we were to stipulate this foundation, and I will not, there are larger problems. Foremost is the question of epistemology. As already mentioned, the contemporary understanding of the demonic is, even if we stick to historically validated methodologies in our study, a matter of interpretation. The very definition of Christian Demonology is the Theological study of demons, which means, essentially, the interpretation of Biblical texts. One needs to ask only a single question, where did the writers of those texts get their information, to see the dilemma. The answer is, of course, by revelation, whatever that may mean. In other words, we find that the entire subject is, outside of this very narrow view, open for debate.

This is not to say that such methods are useless; we shall not progress very far without referring to previous works on the subject. In fact, this study is, in large part, based on the understanding of a series of texts. Rather, however, we wish to be free to consider many more sources (some of which have deeply influenced the thinking of the orthodox theologians) as well as the provenance of these sources. From these texts, we will also consider the assumptions they require, and perhaps find a common ground for the comparison of ideas. Particularly, we will be interested not only in the theological and underlying philosophical views but, hopefully, an understanding of how these things came to be accepted as true. Even more immediate, however, is the issue of how to define the subject.
As noted, the word demonology has been applied to a broad range of concepts and phenomena, from the Greeks (from whom the word comes) to the present. The definition we accept for our study will, as we have seen, have great effect on our final conclusions.

Demonology is not science. Even discussing the word presupposes that there is, in some sense, a ‘reality’ behind it, even if that reality is, as a materialist might think, wholly psychological. We may benefit, therefore, by considering the uses of the word itself.

the Dictionary of Ideas discusses Demonology, beginning with the Greek use of the term.
Greek demonology includes the following religious ideas. There are incorporeal beings differing in rank but all requiring human respect to insure their favor. There is a being called a daimon who is either identical with theos or is the power or agency of theos (Homer). We find that, to the Greeks, the term daimon (from which our word demon is a derived) refers to non-physical beings, incorporeal, which interact with humans. In this case, the daimon does so because it requires ‘respect’, usually in the form of sacrifice of some sort. This is not so very different from what a contemporary theologian might say if asked to define a demon, save that for the Greeks, the moral categorization is absent. While we would probably find a reference to the moral state of the spirit (demons are, after all, fallen angels and angels are good spirits that intercede between God and man) as evil, for the Greeks, they are theos, divine, of themselves or as the agency of the divine, much like the modern concept of angels.
Further; The Pythagorean philosophical idea that there are spirits who are the necessary intermediaries between the gods and men, “because the divine will not mingle directly with the human,” is expressed by Diotima in Plato's Symposium (203A) and is developed by successive Neo-Platonists. It is combined with the notion of the survival of the souls of the dead in the Xenocratic philosophical theory of daimones who are capable of good and evil, are suprahuman but limited, and who dwell near Hades and under the moon. Plato contributes the notion that the heavenly bodies are moved by divine souls, which develops into Aristotle's theory that the planets and stars are moved by “intelligences” (later called “separated substances” in medieval thought) which are perfect and incorporeal—a philosophical answer to the question of the origin of the movement of the heavenly bodies. The idea of a hierarchy of corporeal and incorporeal beings between earth and the outermost border of the world is a philosophical theory of the cosmos in the pseudo-Platonic Epinomis (ca. 347 B.C.?) and later works of the Neo- Platonic school.

We see in this passage an indication of the broad range of ideas that are possible when considering such creatures. Aside from the variety of imagined places where daimons ‘live’ and their tasks or purpose, again there is the concept of daimons as intermediaries between the Divine and the natural world. In fact, as noted earlier, for the ancient Greeks, who believed in a pantheon of gods and goddesses, the daimon could be a god. This is possible since the gods were expressions of the primordial depth or chaos from which the universe itself arose and also personifications of natural forces. This is the definition I wish to use in the current study: the daimon as a spirit that in some sense expresses the being of and mediates the will of Divinity, including those defined as hostile to mankind. This definition allows us to consider beings of considerable power, such as the Greek gods, down to the spirits of nature. Additionally, we will be, I hope, less prone to generalities as we will examine specific examples of Demonological works and consider the author’s perspective, wherever possible, in drawing our own conclusions. To that end, I will set aside any preconception of good or evil in a metaphysical sense, though we will not ignore the fact that many of the spirits discussed in the various writings we shall examine are considered to be inimical to humans.