Revising the discussions made by Georges Canguilhem and Michel Foucault, this study was intended to characterize the conceptual construction of “mental illness” as fully related to social rules. The concept of “illness” involves a socially based judgment about some manifestations which establishes them as inadequate. Often in Medicine, biological data (chemical or physiological), is used to judge difference as illness. In Mental Health, on the other hand, the rules used to define the pathological cannot be supported by biological data - they are clearly situated in the field of values. Mental illness, correlated to abnormality, is defined according to the social rules, and these concepts are applied to those who do not submit to these rules. In this sense, the goal of mental treatments would be the normalization of individuals, adapting them to these rules. Through ethical reflection however, it is possible for the field of Mental Health to go beyond social adaptation, making possible the expression of difference and creativity. Keywords: mental health; normalization; mental treatment; difference.