 The formulation in (P.12ξ,3) is the natural compromise. Informally, it says that for any pair of suitably ξ-related entities x and y there is something that overlaps exactly those things that overlap either x or y. This is strong enough to rule out the model on the left, but weak enough to be compatible with the model on the right. Note, however, that if the Strong Supplementation axiom (P.5) holds, then (P.12ξ,3) is equivalent to (P.12ξ,2). Moreover, it turns out that if the stronger Complementation axiom (P.6) holds, then all of these principles are trivially satisfied in any domain in which there is a universal entity: in that case, regardless of ξ, the sum of any two entities is just the complement of the difference between the complement of one minus the other. (Such is the strength of (P.6), a genuine cross between decomposition and composition principles.)