Originally proposed by John Rawls, the idea of reasoning from conjecture is popular among the proponents of political liberalism in normative political theory. Reasoning from conjecture consists in discussing with fellow citizens who are attracted to illiberal and antidemocratic ideas by focusing on their religious or otherwise comprehensive doctrines, attempting to convince them that such doctrines actually call for loyalty to liberal democracy. Our goal is to criticise reasoning from conjecture as a tool aimed at persuasion and, in turn, at improving the stability of liberal democratic institutions. To pursue this goal, we use as case study real-world efforts to counter-radicalise at-risk Muslim citizens, which, at first glance, reasoning from conjecture seems well-placed to contribute to. This case study helps us to argue that the supporters of reasoning from conjecture over-intellectualise opposition to liberal democracy and what societies can do to counter it. Specifically, they (i) underestimate how few members of society can effectively perform reasoning from conjecture; (ii) overlook that the burdens of judgement, a key notion for political liberals, highlight how dim the prospects of reasoning from conjecture are and (iii) do not pay attention to the causes of religious persons’ opposition to liberal democracy. However, not everything is lost for political liberals, provided that they redirect attention to different and under-researched resources contained in Rawls’s theory. In closing, we briefly explain how such resources are much better placed than reasoning from conjecture to provide guidance relative to counter-radicalisation in societies (i) populated by persons who do not generally hold anything close to a fully worked out and internally consistent comprehensive doctrine and (ii) where political institutions should take responsibility for at least part of the existing alienation from liberal democratic values.