 Finally, Dorr, Hawthorne, and Yli-Vakkuri 2021 propose that, in some cases, the combination of (classical) transworld identity, tolerance, and the restriction principle can all be retained, yet without denying (as do Chandler and Salmon) the transitivity of accessibility between possible worlds. They appeal to two principles: a metaphysical principle of ‘plenitude’ and a metasemantic principle of ‘semantic plasticity’ (for the relevant terms). This solution is defended by Dorr et al partly by considering difficulties for rival solutions (including that of Chandler and Salmon). The details are complex, however: interested readers should consult Dorr et al 2021. As with other proposed solutions to the puzzle, the principles to which Dorr et al appeal (plenitude and semantic plasticity for the relevant terms) are controversial.