Conventional accounts of the path of constitutional equality in the United States conceptualize its development as a trajectory – secular, long-term, and linear. Some find a creedal commitment to equality present, if not realized, from the nation's inception, articulated, for instance, in the Declaration of Indepen-dence's pronouncement “We hold these truths to be self-evident, that all men are created equal.” Others hold the accommodations and protections the Constitution afforded to chattel slavery or to economic elites, among other failings, to have rendered this pronouncement a nullity, if not a mockery. Still others acknowledge the initial statement's significance as an articulated abstraction and dimly apprehended aspiration while shifting the primary focus to the unruly, outsider political and social movements that fought to realize its promise: Jacksonian democracy, abolitionism, first-wave feminism, the labor and Granger movements, populism, progressivism, socialism, New Deal liberalism, second-wave Feminism, civil rights, black power, and the gay rights movement, among others. The Civil War Amendments, particularly the Fourteenth Amendment's guarantee that no state shall deprive any person of the “equal protection of the laws,” belatedly inscribed the commitment to equality in the Constitution's text.
Some interpreters have read that clause narrowly and formalistically, by the lights of an “anti-classification” or “anti-differentiation” principle that guarantees only formal equality under law. Others have read it broadly and aspirationally, as promising substantive fairness, by the lights of an “anti-subordination” or anti-caste principle rooted in robust understandings of civic equality in fact. In either case, the Civil War Amendments marked a significant stride forward. Progress was an “unsteady march,” but the road was at least discernable.
These same accounts map this forward movement along a set of well-known political and legal/doctrinal dimensions. New claims were made for the equality principle's applicability to previously unseen or unacknowledged classifications, once assumed to be natural or self-evidently relevant and rationally related to legitimate public objectives but, in time, newly held to be disturbingly, and perhaps illegitimately, “suspect.” Across time, new claims challenged the disparate treatment of men without property; the poor; women; and racial, ethnic, sexual, gender, and linguistic minorities. Assessments of the legitimacy of these claims involved an acknowledgment, first, of the fundamental and cognizable likeness of all within the class and, second, of the problematic nature of government's disparate treatment between those within and those outside it.