A central and necessary building block for the justification of psychiatric coercion is the identification of a mental illness or mental disorder. This chapter examines the question of how valid the identification of mental disorders is. This begins with the question of whether people have a psyche or a consciousness at all and addresses the problem of drawing the line between “healthy” and “ill”. It is concluded that the current scientific definition does not provide a valid background for the identification of an illness and that there is therefore no elementary justification for the use of coercion in psychiatry.