Demonology hasn’t exactly been a hot topic in Jewish learning circles for the past few centuries. Still, belief in demons was once widespread—even mainstream—until relatively modern times. The Talmud has plenty of references to them, and you’ll find scattered mentions throughout the Bible as well.
One of the more surprising voices in this realm is Rabbi Ovadia Sforno, the famously concise 16th-century scholar and physician. In a rare move, Sforno spends considerable time describing the nature and habits of what many today would call purely mythical creatures.
In Leviticus 17:7, the Torah states:
“And they shall no longer offer their sacrifices to the se’irim (demons) after whom they stray…”
Sforno notes that while the Israelites didn’t worship demons per se, they did occasionally try to contract their services—like supernatural couriers capable of delivering messages across vast distances (a sort of ancient, ethically murky telecommunication system?).
He references the Talmud (Chagigah 16a), which teaches:
“Demons can travel from one end of the world to the other, they know the future, they eat, drink, reproduce, and die.”
Not content with leaving it at that, Sforno attempts a scientific explanation. He writes that demons must be composed of an ultra-refined, invisible substance that allows them to perceive—but not be perceived. Since they consume food, their diet must also be incredibly subtle—perhaps something like the vapor of blood, which he identifies as the carrier of the life force (what we might now call oxygen!). As the Torah states: “For the blood is the life” (Deuteronomy 12:23).
According to Sforno, demons feed off blood—but only when someone spills it for them. In return, they become indebted to that person. They’re also apparently drawn to people who consume blood themselves, since their dispositions align (proto-vampires?).
All of this builds to a firm warning: demons, whatever their substance, are bad news. The Torah, knowing this, includes laws like covering the blood of a slaughtered animal, which Sforno suggests is one of many divine strategies to help keep us safe and at a respectful distance.
Later Chasidic lore adds a curious epilogue. According to tradition, the Baal Shem Tov orchestrated—via divine intervention—the removal of demons from our world entirely. If true, that might help explain why they haven’t been very active lately.
Still, whether real or imagined, ancient or symbolic, we’d all do well to keep our demons—whatever form they take—at bay.
Shabbat Shalom
