The concept of identity claims the virtue that, unlike 'reductionist' or 'essentialist' notions such as class, it can encompass - equally and without prejudice or privilege - everything from gender to class, from ethnicity or race to sexual preference. The 'politics of identity', then, purports to be both more fine-tuned in its sensitivity to the complexity of human experience and more inclusive in its emancipatory sweep than the old politics of socialism.
The laden phrase “identity politics” has come to signify a wide range of political activity and theorizing founded in the shared experiences of injustice by members of certain social groups. Rather than organizing solely around belief systems, programmatic manifestos, or party affiliation, identity political formations typically aim to secure the political freedom of a specific constituency marginalized within its larger context. Members of that constituency assert or reclaim ways of understanding their distinctiveness that challenge dominant oppressive characterizations, with the goal of greater self-determination. (From Stanford Encyclopedia of Philosophy) What is crucial about the “identity” of identity politics appears to be the experience of the subject, especially his or her experience of oppression and the possibility of a shared and more authentic or self-determined alternative.
It is easy to see how critics of identity politics, and even some cautious supporters, have feared that it is prone to essentialism, another philosophical term of abuse. Either the defining features one-dimensional, as if being Asian-American, for example, were entirely separable from being a woman, or generalizations made about particular social groups in the context of identity politics may come to have a disciplinary function within the group, not just describing but also dictating the self-understanding that its members should have.
Racism attempts to reduce members of social groups to their racial features, drawing on a complex history of racial stereotypes to do so. Advocates of color-consciousness argue that racism will not disappear without proactive efforts, which require the invocation of race. Thus affirmative action, for example, requires racial identification and categorization, and those working against racism face a paradox familiar in identity politics: the very identity they aim to dispel must be invoked to make their case. Without recourse to the white masculine middle-class ideal, politicized identities would forfeit a good deal of their claims to injury and exclusion, their claims to the political significance of their difference. (Wendy Brown, States of Injury)
For Wendy Brown, following Nietzche, the wounds that underlie the politics of identity lead to ressentiment, a powerless over the past— a past of injury, a past as a hurt will, as a "reason" for the "unendurable pain" of social powerlessness in the present.