Incarceration in prisons and mental hospitals are clear instances of deprivation of liberty. The former is justified by the prisoner’s guilt, the latter by the patient’s mental illness. Crime implies injury to the life, liberty, or property of others. Mental illness implies “dangerousness” to self or others and non-responsibility for one’s (mis)behavior. These truisms frame the context for my criticism of many libertarians’ acceptance of the concept of mental illness, which constitutes the vital center of the ideology of mental health.