If politics is all about power, then liberalism – as a normative political philosophy, with aspirations to rationality and justice – arguably doesn’t get off the ground. The need to restrain power in politics is sometimes understood – for instance, and in very different ways, by political realists and by political liberals – as also requiring heavy constraints on the political relevance of truth: Relying on the truth – of a moral principle, for instance – in the face of disagreement about it is sometimes presented as a mere power-play, motivating the search for a political philosophy in which the notion of truth does not do any work (and is replaced, say, by a notion of reasonableness) (Rawls 1996). If a comprehensive liberalism is to be defended, then, it must have something to say about the truth of its underlying principles and values, but also about how relying on them avoids reducing to a mere exercise of arbitrary power.

Even just within the bounds of the Rawlsian version of Political Liberalism, there is a discussion as to whether some notion of truth is theoretically indispensable, or whether everything can be done using reasonableness instead (Estlund Manuscript). Once we go wider within liberalism – beyond the scope of Political Liberalism – further questions arise: What is the relation between truth (of, say, a moral principle, or a claim about the good life) and political legitimacy? Is legitimate political authority grounded in something like the likelihood of the authority getting things right (with regard to advisable policies, or in helping subjects adhere to the reasons already applying to them: Raz 1986, Viehoff 2011, Enoch 2014), or is this kind of consideration not relevant to establishing authority (Darwall 2009; 2010; Hershovitz 2011), and authority is grounded in a way that is, as it were, further from the relation to truth, perhaps in reasonableness (Rawls 1996)? Or perhaps authority – in general, or in the specific case of democratic authority – is grounded in a combination of epistemic and other considerations, like perhaps a politically qualified epistemology (Estlund 2009) or a pragmatic epistemic justification of democratic deliberation (Talisse 2021)? 

Consider, by way of an example of the work to be done here, the following: Liberals – certainly, comprehensive liberals – aspire to universality and rationality, and so typically claim a very strong status for the underlying liberal principles themselves (perhaps equality and autonomy, properly understood). Still, as all liberals should acknowledge, in the real world such principles are bound to be controversial. Even if such controversy does not in any way undermine the truth of such principles (Enoch 2011), and even if Rawlsians are mistaken about at least some of the implications of such controversy (Enoch 2015), surely it gives rise to the following problem: How can the liberal justify, consistently with underlying liberal principles, the state using its coercive power vis-à-vis those who reject such principles? Even while insisting on these principles’ universal and necessary truth, then, the liberal – who is committed to the values of liberty and autonomy, and who therefore sees all coercion as pro tanto objectionable – cannot accept the truth of principles as sufficient grounds for their enforcement. On the other hand, the liberal must insist, it seems, that the truth of principles is at least relevant for the justification of political action based on them. So the liberal must develop an account of autonomy and legitimacy that will allow truth to play a role, but not all on its own, in grounding the legitimacy of autonomy-restricting political action.