The theory of “disinhibition” has been very influential in psychiatry and neurology for over a century. Disinhibition has been used to explain clinical findings in many neurological and psychiatric disorders including dementia, traumatic brain injury, attention deficit hyperactive disorder, substance abuse, impulsivity in personality disorders, and neurodevelopmental disorders. In addition, disinhibition has been used as a unifying theory to link clinical observations with cognitive findings, and even cellular findings. This review discusses the origins and history of the theory of disinhibition and its strengths and weaknesses in four domains: face validity, consistency with other brain mechanisms, consistency with evolutionary mechanisms, and empiric support. I assert that the vagueness of the theory, inconsistency with other brain mechanisms, and lack of empiric support limit the usefulness of this theory. Alternative approaches, based on findings in other motor, language, and cognitive functions, are discussed.