The Occupational Safety and Health Act contains one sentence that does more regulatory work than the thousands of pages of standards that follow it. Section 5(a)(1) requires every employer to keep the workplace free of recognized hazards likely to cause death or serious physical harm, and it is how OSHA reaches combustible dust, excessive heat, workplace violence, and ergonomic injury without ever having promulgated a standard for any of them. This article explains the four elements the Secretary must prove, why industry recognition and feasible abatement decide most contested cases, and why the clause is unavailable whenever a specific standard already addresses the hazard. It works through the modern battlegrounds where general duty enforcement is doing the job that rulemaking has not, and through the defenses that beat these citations at the Review Commission. It closes with the harder question underneath: whether a statute that requires employers to guess at unwritten obligations, enforced case by case, is regulation or something less orderly, and what a compliance program should do about it either way.