The “psychogenic inference” is the inference that if there is no known physical cause for a symptom or disorder, the cause must be psychological. Although this inference is commonly made, this paper argues that it is a Siren song; that, although superficially appealing, it faces many serious objections, leads to “overpsychologizing”—the overdiagnosis of psychological problems—does much harm and should now be finally eliminated. It should be replaced by two key diagnostic principles and an open question. Using methods of linguistic analysis, the paper shows that the inference is systematically entrenched in the key terms functional, nonorganic, and somatization and in the established criteria for somatoform disorders. The forthcoming revisions of DSM-IV-TR and ICD-10 present a unique opportunity to eliminate the inference, to introduce unambiguous, untainted, and patient-friendly terminology, and to replace defective classificatory criteria. The opportunity needs to be grasped. Decisive action taken now will bring great rewards.