No pile of facts about how the world is can, by logic alone, tell you how it ought to be

Hume pointed out that moral arguments routinely slide from describing the world to prescribing how we should act, without ever justifying the leap. Later philosophers called this gap 'Hume's Guillotine,' and it remains a central problem for anyone trying to ground ethics in pure observation.

— David Hume, A Treatise of Human Nature — Book III, Part I, Section I, 1739