Pragmatic theories of truth need to pass the pragmatic test: they need to make a difference. Unfortunately, defenders of the pragmatic theory have rarely applied this test. I argue that a Deweyan pragmatic account of truth passes the test by identifying the political and epistemic dangers of certain types of social networks that create a durable consensus around false beliefs. To better understand Dewey’s account of truth I propose an excursion through Wittgenstein’s later views on knowledge and certainty.