Once created, institutions often change in subtle and gradual ways over time. Although less dramatic than abrupt and wholesale transformations, these slow and piecemeal changes can be equally consequential for patterning human behavior and for shaping substantive political outcomes. Consider, for example, the British House of Lords. This is an institution that began to take shape in the thirteenth century out of informal consultations between the Crown and powerful landowners. By the early nineteenth century, membership was hereditary and the chamber was fully institutionalized at the center of British politics. Who would have thought that this deeply undemocratic assembly of aristocrats would survive the transition to democracy? Not the early Labour Party, which was founded in 1900 and understandably committed to the elimination of a chamber from which its constituents were, more or less by definition, excluded.

Yet Labour did not dismantle the House of Lords – despite recurring opportunities to do so during the twentieth century. Instead, the institution was reformed over time in a series of more measured moves that, successively: circumscribed its powers (especially in 1911 by a Liberal Party government), altered its composition (especially in 1958 under a Conservative government, with the addition of life peerages), and rendered it less unwieldy and – in the eyes of some – more legitimate (in 2000 under a Labour government, by reducing dramatically the number of hereditary peers).