The concept of discrimination does many different kinds of work in the law, across the entire range of abstraction, from specific prohibitions to general principles. Prohibitions framed generally in terms of discrimination augment more specific prohibitions, which go into great detail about what the law requires, of whom, in what circumstances, and with what exceptions. Discrimination serves as the organizing principle for these statutory provisions, and numerous others, connecting them to still more general principles of equality and justice. Most scholars regard the concept of discrimination as a bridge leading from concrete rules to abstract ideals. This essay goes in the opposite direction, back toward the narrow and intricate legal prohibitions that have grown up over nearly half a century, as discrimination has changed from a rallying cry for social movements to an institutionalized program of regulation. It serves as an inclusive label for such programs, but its operative effect turns out to be far more qualified and elusive. It occupies the uneasy middle ground between the abstractions of equality, liberty, and other ultimate aims attributable to a legal system, and the intricacies of legal doctrine and the practicalities of enforcement, administration, and compliance. It is the latter, this essay contends, that often determine the scope and content of prohibitions against discrimination, as in disputes over liability for disparate impact, coverage of additional grounds of discrimination, and attempts to counteract implicit bias.