 The idea is that knowledge requires a margin for error, a margin of at least one jellybean in our example. Presumably more than one jellybean, but at least one. Within one jellybean of the true number, you can’t discern truth from falsehood. (See Nozick (1981) for a different conception of a “no luck” requirement on knowledge, which Roush (2005; 2009) formalizes in probabilistic terms.)