 Where an option O aims to avert a threat T, we determine O’s necessity by comparing it with all the other options that will either mitigate or avert T. We determine its proportionality by comparing it with the harm suffered if T should come about. The only difference between the proportionality and necessity constraints is that the former involves comparing one’s action with a very specific counterfactual scenario—in which we don’t act to avert the threat—while the latter involves comparing it with all your available options that have some prospect of averting or mitigating the threat. In my view, we should simply expand this so that the necessity constraint compares all your available options bar none. Then proportionality would essentially involve comparing each option with the alternative of doing nothing, while necessity would involve comparing all options (including doing nothing) in terms of their respective balances of goods and bads. On this approach, necessity would subsume proportionality. But this is a technical point with little substantive payoff.