The Bell-Kochen-Specker family of paradoxes (Bell 1966; Kochen &amp; Specker 1967) are based on a relatively simple idea, although its execution is sometimes complicated: if one chains together a sufficient number of incompatible frameworks it is possible to arrive at a logical contradiction. The chaining consists in finding a projector which belongs to two (or more) incompatible decompositions of the identity, and then assuming it has the same truth value in both frameworks, whereas in any single decomposition one and only one projector is true. The histories approach blocks paradoxes of this sort because they (obviously) violate the single framework rule. See the Further Reading supplement for details. Griffiths (2002a).--> 