The future similarity objection against David Lewis’s theory of counterfactuals re-emerges once the space-time of possible worlds is adequately represented. Given such a representation, it can be shown that a number of counterfactuals that seem clearly true, such as Kit Fine’s example ‘If Nixon had pressed the button, there would have been a nuclear holocaust’, come out false, even if determinism is assumed. Lewis’s similarity criteria can be modified in different ways to avoid the problem, but some of the modifications have problems of their own.