The merits of these competing theories are of mainly academic concern. When people debate whether there were weapons of mass destruction in Saddam Hussain’s Iraq, whether global warming is real and anthropogenic, or whether austerity is necessary, their disagreements are not the consequence of competing theories of truth. No witness need ask a judge which theory she has in mind when asked to promise to tell the truth, the whole truth and nothing but the truth. Why then has truth become so problematic in the world outside academic philosophy? One reason is that there is major disagreement and uncertainty concerning what counts as a reliable source of truth. For most of human history, there was some stable combination of trust in religious texts and leaders, learned experts and the enduring folk wisdom called common sense. Now, it seems, virtually nothing is universally taken as an authority. This leaves us having to pick our own experts or simply to trust our guts.