For political realists, legitimacy is a central requirement for the desirability of
political institutions. Their detractors contend that it is either descriptive, and
thus devoid of critical potential, or it relies on some moralist value that realists
reject. We defend a functionalist reading of realist legitimacy: descriptive legitimacy,
that is, the capacity of a political institution to generate beliefs in its right
to rule as opposed to commanding through coercion alone, is desirable in virtue of
its functional role. First, descriptive legitimacy plays an evaluative role: Institutions
can fail to convince citizens that they have a right to rule and can be ranked by
how well they do so. Second, descriptive legitimacy plays a normative role, because
if an institution fails to convince subjects of its right to rule, this gives them
a reason not to comply with its directives, even if it satisfies philosophers’ standards
for possessing such right.
