What Is Mental Illness?

The concept of mental illness has been challenged by various parties and with various background concerns. In this paper, I will discuss how mental illness is defined, as far as it is considered as a title to special treatment. The essentialism about mental illness insists that mental illness is distinguished from other harmful human conditions by some scientific criteria. Three essentialistic theories―physical lesion, biological disadvantage,and evolutionary dysfunction theories―are reviewed, and it is shown that they all fail to appropriately distinguish illness from normality. I will alternatively defend the anti-essentialism about mental illness,which characterize mental illness as harmful human conditions that are best treated by psychiatric professionals.