A new nosology for mental disorders is needed as a basis for effective scientific inquiry. Diagnostic and Statistical Manual of Mental Disorders and International Classification of Diseases diagnoses are not natural, biological categories, and these diagnostic systems do not address mental phenomena that exist on a spectrum. Advances in neuroscience offer the hope of breakthroughs for diagnosing and treating major mental illness in the future. At present, a neuroscience-based understanding of brain/behavior relationships can reshape clinical thinking. Neuroscience literacy allows psychiatrists to formulate biologically informed psychological theories, to follow neuroscientific literature pertinent to psychiatry, and to embark on a path toward neurologically informed clinical thinking that can help move the field away from Diagnostic and Statistical Manual of Mental Disorders and International Classification of Diseases conceptualizations. Psychiatrists are urged to work toward attaining neuroscience literacy to prepare for and contribute to the development of a new nosology.