To explain the inner workings of mass incarceration and systemic racism more generally, Alexander borrows a metaphor from American philosopher Marilyn Frye, who likens racism to a birdcage. Paraphrasing Frye, Alexander writes:

If one thinks about racism by examining only one wire of the cage, or one form of disadvantage, it is difficult to understand how and why the bird is trapped. Only a large number of wires arranged in a specific way, and connected to one another, serve to enclose the bird and to ensure that it cannot escape (228).

Aside from the fact that the subject of Alexander’s book is literal cages, the metaphor is very fitting for her purposes. During Jim Crow, Americans were trained to understand racism only in its most virulent and explicit forms. Thus, when Americans look to only one court case involving policing, presumably decided on race-neutral grounds; or only one piece of legislation calling for increased police funding, presumably to keep the streets safe; or only one media story, calling attention to a crime committed by a Black man, they do not see racism. Yet when one considers all these factors as intricately connected strands of a larger system that causes grossly disproportionate racial outcomes, the metaphysical cage becomes as easy to recognize as a literal cage.