Like everything with Foucault, there are many different approaches in answering this question. The first would be the notion of division and exclusion in society. Blanche is declared "mad," in large part, because she is different. As Williams would write in another play, "too rare to be normal." Her institutionalization is because she is "different." Stanley angles for Blanche to be institutionalized through her sister in order to consolidate his own power and not be threatened with Blanche and the formidable hold she had on her sister. In using mental illness as a reason to commit her, one sees the Foucaudian idea of being able to manipulate mental illness as a way to foster division between society and the individual. Like the genealogy offered in Foucault's work where there is a strict division of those who are "accepted" and those who are rejected, the idea of the insane person as being isolated as a way to consolidate the prevailing social order's conception of power is one that is replicated with Blanche's own institutionalization.