The following is an excerpt from Russell’s book Mephistopleles: The Devil in the Modern World (1986)

History at its best opens our minds to unfamiliar modes of thought rather than mining the past for data to fit our own preconceptions. It avoids the odd assumption that the predominant world view of our own time is somehow forever true. But modern historians find themselves in a dilemma. On the one hand, they are drawn toward materialism. On the other hand, and more powerfully, they are drawn toward relativism, and that relativism, oddly, also leads them to accept materialism, since that is the most common viewpoint of the late twentieth century and is the basis for most of the new methodological vogues: it is “where the action is.” Materialist history has produced much that is of value, but it also suffers from limitations, the first of which is that there is no compelling philosophical reason to assume the priority of materialism over idealism. Ultimate reality is, in other words, at least as likely to be “idea” as “matter.” In considering the Devil, materialist historians begin with the knowledge that the Devil does not exist scientifically and then slide into the assumptions that the Devil therefore does not exist historically; that the idea is outdated by science and therefore silly; that there is no point of studying it in itself; and that its only use lies in helping them understand the “mentalities” that produced it — mentalities formed by the material, social conditions that materialist historians take to be the only realities.

This sort of dilemma can be avoided by taking a more idealist tack. Idealist historians realize that their own world view and that of their contemporaries is as precarious as those of the past; they are therefore willing to learn from the world views of other cultures; and they believe that ideas are important in themselves, affecting material conditions as well as being affected by them, and having a life and meaning of their own. The idea of the Devil is an important concept in understanding the nature of evil, and as such it points toward the truth. The Devil exists historically as a long-lived and immensely influential concept aimed at the truth about evil…..

“The Devil” is best investigated by history, which does not make the faith assumptions of theology yet can, unlike science, address the phenomenon directly. Since the history of the Devil embraces other modes of knowing the Devil, such as theology, mythology, and literature, it is superior to all other approaches in that it includes them all. The Devil is therefore best defined in terms of his history.