Intersectionality as we know it today was given life by Kimberlé Crenshaw, a law professor and social theorist. In the talk that brought the metaphor of the intersection into public discussion, she first noted:*1
in race discrimination cases, discrimination tends to be viewed in terms of sex- or class-privileged Blacks; in sex discrimination cases, the focus is on race- and class-privileged women.
She then explained some of the consequences of this:
This focus on the most privileged group members marginalizes those who are multiply-burdened and obscures claims that cannot be understood as resulting from discrete sources of discrimination. I suggest further that this focus on otherwise-privileged group members creates a distorted analysis of racism and sexism because the operative conceptions of race and sex become grounded in experiences that actually represent only a subset of a much more complex phenomenon
But why not simply include Black voices in feminism and women’s voices in anti-racism and call it good? For Crenshaw, it was because the effects of multiple oppressions are not merely linear increases, not merely additive.