Karl Popper said that if you want to refute someone’s position, you first help them to build up the strongest possible argument for what they believe. Once all the loose ends are tied up, all the grey areas clarified, and your opponent’s argument is as strong as it can possibly can be — only then do you attack it. What’s more, you have to attack it right at its strongest point; that way you can be satisfied that if you do find a refutation, you’ve found a substantial one and you both haven’t been wasting time dancing round the handbags of triviality.
There are many comfortable but ultimately weak arguments against replacing Trident; I propose that we put these on one side and look squarely at the best argument for keeping it.
An example of a comfortable but weak argument would be: money spent on Trident would be better spent on reducing global poverty. This may be true, but the Ministry of Defence isn’t going to vire its nuclear submarine budget over to DFID just like that. So I think we shouldn’t bother making this point.
To be pro-Trident doesn’t mean to be pro-war. The best argument for keeping Trident is that it prevents war by preserving the balance of threat. So it seems to me that this is a debate about the best way to pursue peace (hence the name: nuclearpeace).
Essentially, both sides in this debate believe in deterrence. To argue against the replacement of Trident is to argue that getting rid of it will, in the long run, be a greater deterrent. It has to be argued that disarmament will result in fewer conflicts across the future sweep of history. Can this possibly be true?