A polity is grounded in a modus vivendi (MV) when its main features can be presented as the outcome of a virtually unrestricted bargaining process. Is MV compatible with the consensus-based account of liberal legitimacy, i.e. the view that political authority is well grounded only if the citizenry have in some sense freely consented to its exercise? I show that the attraction of MV for consensus theorists lies mainly in the thought that a MV can be presented as legitimated through a realist account of public justification. Yet I argue that, because of persistent ethical diversity, that realism problematically conflicts with the liberal commitments that underpin the very ideas of consensus and public justification. Thus, despite the interest it has recently attracted from critics of political liberalism and deliberative democracy, MV is not an option for those wishing to ground liberal political authority in some form of consensus. So if realist and agonistic critiques are on target, then the fact that modus vivendi is not an option casts some serious doubt on the viability of the consensus view of liberal legitimacy.
Key words: consensus, legitimacy, liberalism, modus vivendi, realism.
