 By contrast, (P.12ξ,2) corresponds to a notion of sum that may seem too strong. In a way, it says—literally—that any pair of suitably ξ-related entities x and y compose something, in the sense already discussed in connection with (35): they have an upper bound all parts of which overlap either x or y. Thus, it rules out the model on the left of Figure 7, precisely because w is disjoint from both x and y. However, it also rules out the model on the right, which depicts a situation in which z may be viewed as an entity truly made up of x and y insofar as it is ultimately composed of atoms to be found either in x or in y. Of course, such a situation violates the Strong Supplementation principle (P.5), but that's precisely the sense in which (P.12ξ,2) may seem too strong: an anti-extensionalist might want to have a notion of sum that does not presuppose Strong Supplementation.