Clinicians inherit a categorical playbook that implicitly treats diagnoses as natural kinds, yet everyday psychiatry is saturated with comorbidity, diagnostic instability, and weak alignment with biology. What’s missing often is a conceptual orientation that acknowledges dimensional, hierarchical, and dynamic structure while remaining usable in clinic. This lecture supplies that orientation: it shows why neo-Kraepelinian assumptions falter, outlines a pluralistic nosology fit for clinic, and illustrates it with contemporary developments.