Mental illness does not literally exist. It might poetically exist as a metaphorical idea. It is like the idea that a sick joke is not literally sick. The brain can literally be sick - stroke, neurosyphilis, cancer, and so forth. The "mind", like a joke, simply cannot literally be sick unless we use language in inaccurate and imprecise ways. This simply matters because many psychiatrists earn money from psychiatric coercion and justify their actions by claiming mental illness is literally real and effectively turns a person into a non-person (an entity that is not capable of making their own decisions). Similar logic was utilized to justify chattel slavery in America hundreds of years ago (black people are three-fifths of a person, which was in the US Constitution).