In his book The Medicalization of Everyday Life, Szasz compares the idea of mental illness to phlogiston theory. Phlogiston was a theory about combustion and oxidation that was sort of right, but it was ultimately wrong. Oxidation in chemistry took the place of phlogiston theory. Mental illness is sort of correct in describing human misery and distress; however, it is ultimately wrong and incomplete. According to Szasz, mental illness is a metaphor that is improperly literalized – like the Catholic doctrine of transubstantiation. In his book Psychiatry: The Science of Lies, Szasz compares psychiatric diagnoses as diseases to art forgeries; now matter how good a forgery is, it can never be an authentic original of the supposed artist. Mental illness can look like a real disease, however, once a mental illness is proven to be an authentic disease, then such a disease is a neurological disease (a brain pathology), not a mental illness. According to Szasz, the mind is abstract, so it can only be metaphorically ill or diseased.