 One such argument is given by Chandler (1976). It can be illustrated simply as follows (adapting Chandler’s own example). Suppose that there is a bicycle originally composed of three parts: A1, B1, and C1. (We might suppose that A1 is the frame, and B1 and C1 the two wheels.) Suppose we think that any bicycle could have been originally composed of any two thirds of its original parts, with a substitute third component. We may call this (following Forbes 1985) ‘the tolerance principle’; it is a development of the intuitively appealing thought that it is too much to demand, of an object such as a bicycle, that it could not have existed unless all of its original parts had been the same. Suppose, further, that we think that no bicycle could have been originally composed of just one third of its original parts, even with substitutes for the other two thirds. Call this ‘the restriction principle’. The combination of these assumptions appears to generate a difficulty for the paraphrase of de re modal claims about bicycles in terms of transworld identity. For if there is (as the tolerance principle allows) a possible world w2 in which our bicycle comes into existence composed of parts A1 + B1 + C2, where C1 ≠ C2, then, if we apply the tolerance principle to this bicycle we must say that it could have come into existence (in some further possible world w3) with any two thirds of those parts, with a substitute third component: for example, that it could have come into existence (in w3) composed of A1 + B2 + C2, where B1 ≠ B2 and C1 ≠ C2. The bicycle in w3 is, ex hypothesi, identical with the bicycle in w2, and the bicycle in w2 is, ex hypothesi, identical with the original bicycle; so, by the transitivity of identity, the bicycle in w3 is identical with the original bicycle. Hence our assumptions have generated a contradiction. We have a bicycle in w3, originally composed of A1 + B2 + C2, that both is identical with the original bicycle (by the repeated application of the tolerance principle, together with the transitivity of identity) and is not identical with the original bicycle (by the restriction principle).