In recent weeks assertions have been made in various media forums that the Iranian regime is irrational, and that therefore we cannot expect them to be deterred from using nuclear weapons against the US and its allies. I find these assertions highly dubious, in part because similar claims have been made regarding every new nuclear power since the 1940s, which all proved false, and in part because the Iranian regime strikes me as extremely crafty. However, it still provides an excuse to revisit the old question of how useful deterrence is against irrational actors.
In order to avoid bringing politics into the mix, I am going to posit a scenario involving a non-political irrational actor. This actor is someone you may or may not be familiar with- homeless mentally ill exhibitionist man. Fifty years ago he would have lived in the state mental hospital, but thanks to deinstitutionalization we get to see him every day on the way to work. Although I'm not offended by nudity myself and think he's in terrible need of help, apparently our societal priorities are elsewhere. The important thing is that we protect our young people from seeing a grown man's penis at any cost.
Now, in the real world, we would expect that HMIEM would be regularly arrested by the police, and perhaps incarcerated for an extended period of time depending on state and local statues. But that implies a power disparity that is not useful for this discussion, so I'm going to assume that HMIEM has diplomatic immunity. Therefore, the "community" has to enforce its "standards" by non-legal means. (Jurisprudence is such a boring cop-out, after all!)
Because HMIEM is legally untouchable, we need to find our own way to deter him from exposing his genitals to passerby. For fun, let's try to develop a means of deterrence based on the lessons of the Cold War nuclear arms race. For instance, I could attemp to expose HMIEM to the same threat he poses us. Can MAE (Mutually Assured Exposure) deter homeless mentally ill exhibitionist man?
We don't know. Just as we can't be absolutely sure that a mentally unstable dictator doesn't have a death wish, we cannot be sure that homeless mentally ill exhibitionist man doesn't enjoy the sight of another man's member. He likes to show his off, after all. It's possible that despite his exhibitionist tendencies, HMIEM will be so offended by the prospect that he will be deterred, but this seems unlikely. We cannot project our own fears and motivations unto him. We cannot assume that he feels shame or fear of death. Instead, we must come to understand his motivations. This might prove problematic, seeing as he is seriously disturbed, but we are obligated to try as a means to manage the situation. If we're lucky, we'll find a cheap, easy solution to the problem. But in the end, there is no guarantee that we can dissuade homeless mentally ill exhibitionist man from exposing himself to us.
Fortunately, the world's nuclear arsenals aren't managed by HMIEM. For the past 60 years, leaders charged with setting nuclear policies have been rational, generally well-meaning men. But this is no guarantee that this will always be the case. There is always a distant possibility that a genuine lunatic will gain control of one or more nukes. But this is not likely. We need to worry less about "deterring the insane" and more about deterring the "rational."