Demonology represents a fascinating case of evolving beliefs among Jews. While once widespread, explicit belief in demons has become limited to distinct groups. The question whether Judaism endorses such a view, however, has been a heated debate for many centuries.In a few passages, the Bible disparages non-Jews who worship demons. “They sacrificed to demons, not gods, gods they had never known” (Deuteronomy 32:17). These passages might contend the Torah denies the existence of demons, or alternatively acknowledges their existence but disparages their worship. The latter approach was seemingly adopted in the Talmud, which contains extensive discussions regarding the origin and nature of these evil spirits.In legal contexts, the Sages banned consuming things in pairs for fear of demonic harm, while discussing whether an admonition issued by a demon makes a sinner liable to punishment. Additionally, rabbinic literature attests to scholars performing exorcisms.As Rabbi Natan Slifkin has documented, many medieval rationalists denied the existence of demons. Maimonides and Gersonides all contended that this belief was false or illusory. Rabbi Yaakov Anatoli lamented that many Jews, laypeople and scholars alike, believed in such “nonsense,” while one Provencal scholar, Rabbi Levi ben Avraham of Villefranche declared, “An enlightened person should not believe everything he is told, even if the person telling it is a scholar and pious person.”Yet he also stated one should believe all matters accepted from our prophets and sages, thereby raising the question of how to interpret the sources which seemingly affirm the existence of demons. To solve this problem, Rabbi Menachem Hameiri regularly interpreted the talmudic passages as referring to evil thoughts or psychosomatic problems, but not objective entities, also contending that this debate should be decided by empirical investigation.These approaches were thoroughly scorned by many medieval scholars, who believed Jewish tradition clearly affirmed the existence of demons. Figures like Rabbi Yehuda Halevi and Moshe Taku lambasted those who abandoned a clear-cut rabbinic belief because of their philosophical inclinations, with the latter even declaring that Rabbi Avraham Ibn Ezra was killed by demonic dogs because he denied their existence.Centuries later, the Vilna Gaon decried that Maimonides had been “led astray by accursed philosophy” to deny demons, amulets and other occult phenomena. Beyond invoking tradition, Nahmanides asserted there was eyewitness testimony for their existence, even as they generally possessed undetectable bodies.Demonology was a hallmark of kabbalistic and other mystical literature. Yet even a couple of philosophers, including Rabbi Hasdai Crescas, affirmed (esoteric) knowledge of demons with a combination of rationalizations and appeals to tradition. In the 17th century, Rabbi Menasseh ben Israel asserted he saw no difference in affirming the existence of God or demons, both of which were invisible entities attested to by tradition. A few scholars denied the existence of demons, yet maintained the Sages had not erred. One prominent strand, adopted by Rabbi Shlomo Luria but already anticipated in early medieval texts, asserted that demons and evil spirits were prevalent in antiquity but no longer existed. This position allowed many halachists to circumvent any laws relating to demons without having to nullify them. Rabbi Menachem Mendel of Kotzk even allegedly maintained demons existed, until Maimonides denied their reality – at which point God, in respect to this scholarly master, indeed removed them from the world! In the 19th century, Rabbi Samson Raphael Hirsch contended this dispute was irresolvable, and that people may adopt either position, since they must anyway distance themselves from engaging in the occult. Many traditionalists, I suspect, have taken this route which, consciously or otherwise, allows them to subtly reject demonology without having to disavow passages in classic rabbinic texts.Yet such an approach might prevent contemporary believers from confronting an important challenge to faith. Many scholars rejected demonology because they found alternative naturalistic explanations for many phenomena in contemporary science. The mechanic universe depicted by modern science, however, also poses a threat to the belief in anything supernatural or divine.Confronting demonology presents the opportunity of affirming our belief in God, even as we accept the findings of modern science. The writer teaches at Yeshivat Hakotel, directs the Tikvah Israel Seminars for posthigh school students, and is a junior research fellow at the Israel Democracy Institute.