" The claim that “mental illnesses are diagnosable disorders of the brain” is not based on scientific research; it is a lie, an error, or a naive revival of the somatic premise of the long-discredited humoral theory of disease. My claim that mental illnesses are fictitious illnesses is also not based on scientific research; it rests on the materialist-scientific definition of illness as a pathological alteration of cells, tissues, and organs. If we accept this scientific definition of disease, then it follows that mental illness is a metaphor, and that asserting that view is asserting an analytic truth, not subject to empirical falsification. "

― Thomas Szasz , The Myth of Mental Illness: Foundations of a Theory of Personal Conduct