Hume’s Guillotine is a fancy name for a simple idea: you can’t say what people should do just by looking at what is happening. Imagine someone says, “People are mean to each other, so being mean must be okay.” That’s jumping from a descriptive statement (what is) to a normative statement (what ought to be), and Hume’s Guillotine says you can’t do that without adding a moral reason.
A descriptive statement just tells you facts, like “Lying happens every day.” But if you want to say “Lying is wrong,” that’s a normative statement—it tells people how they should behave. To connect the two, you need a moral bridge, like “Hurting people is bad.” Without that extra piece, the logic doesn’t hold up.
Philosophers use this rule to keep arguments clear and honest, so we don’t sneak in moral judgments without saying where they come from. Hume’s Guillotine helps us notice when someone tries to skip a step and go from facts to rules without explaining why we should care—and that’s super helpful when we’re trying to figure out what’s right or wrong.