At the core of political liberalism is the claim that political institutions must be publicly justified or justifiable to be legitimate. What explains the significance of public justification? The main argument that defenders of political liberalism present is an argument from disagreement: the irreducible pluralism that is characteristic of democratic societies requires a mode of justification that lies in between a narrowly political solution based on actual acceptance and a traditional moral solution based on justification from the third-person perspective. But why should we take disagreements seriously? This—epistemic question—has not received the attention it deserves so far. I argue that the significance of public justification can be explained through the possibility of reasonable disagreement. In a reasonable disagreement, the parties hold mutually incompatible beliefs, but each is justified to hold the belief they do. I shall use the notion of a reasonable disagreement to explain the possibility of an irreducible pluralism of moral and religious doctrines and, on that basis, why the justification of political institutions has to be public.
See David Christensen“Epistemology of Disagreement: The Good News,”Philosophical Review116 (2007): 187-217; Elga “Reflection and Disagreement” and Richard Feldman “Reasonable Religious Disagreements” in Louise Antony (ed.) Philosophers Without Gods: Meditations on Atheism and the Secular (Oxford: Oxford University Press 2007) 194—214.
Goldman“Epistemic Relativism and Reasonable Disagreement” p. 201describes the resulting position—he calls it “objectivity-based relativism” as follows: “There is a uniquely correct E-system that governs the objective justifiedness and unjustifiedness of people’s doxastic attitudes. However people occupy different evidential positions vis-a-vis this system and other candidate E-systems. Hence the objective justificational status of different people vis-a-vis different E-systems is varied rather than uniform. Some people are objectively justified in believing certain E-norms and E-systems to be correct; others are objectively justified in believing other E-norms and E-systems to be correct. Similarly for attitudes other than full belief toward E-norm-related propositions.”