Should you reduce your energy consumption? Tragically enough, it may be better for you, and for everyone involved, to refrain from doing so even if you care about the climate. Given this tragedy, why cooperate? This paper defends the view that not cooperating is morally problematic because it is not universalizable (in a Kantian sense). That is, I will argue that we have universalizability-based reasons to cooperate as long as we have a preference for ‘collective success’ (e.g. a sustainable planet). (...) The problem is that defectors let others fix the problem for them, and in this way make an unfair exception of themselves. Moreover, even when selected agents might not share this preference, they still have to cooperate for the sake of others. (shrink)