Is this rationality, or the politics of two-year-olds with nukes?
Is this a constructive point, or just more gesturing?
It is a gesture concluding a constructive point.
You're very focused on Wei Dai's statement about backward induction, but I think you're missing a key point: His strategy does not depend on D reasoning the way he expects them to, it's just heavily optimized for this outcome. I believe he's right to say that backward induction should convince D to comply, in the sense that it is in their own best interest to do so.
This is a distinction without a difference. If H bombs D, H has lost (and D has lost more).
If both countries precommit, D gets bombed until it halts or otherwise cannot continue development.
That depends on who precommits "first". That's a problematic concept for rational actors who have plenty of time to model each others' possible strategies in advance of taking action. If H, without even being informed of it by D, considers this possible precommitment strategy of D, is it still rational for H to persist and threaten D anyway? Or perhaps H can precommit to ignoring such a precommitment by D? Or should D already have anticipated H's original threat and backed down in advance of the threat ever having been made? I am reminded of the Forbidden Topic. Counterfactual blackmail isn't just for superintelligences. As I asked before, does the decision theory exist yet to handle self-modifying agents modelling themselves and others, demonstrating how real actions can arise from this seething mass of virtual possibilities?
Then also, in what you dismiss as "messy real-world noise", there may be a lot of other things D might do, such as fomenting insurrection in H, or sharing their research with every other country besides H (and blaming foreign spies), or assassinating H's leader, or doing any and all of these while overtly appearing to back down.
The moment H makes that threat, the whole world is H's enemy. H has declared a war that it hopes to win by the mere possession of overwhelming force.
Speaking of nuclear proliferation and its consequences, you've been pretty silent on this topic considering that preventing proliferation is the entire motivation for Wei Dai's strategy. Talking about "murdering millions" without at least framing it alongside the horror of proliferation is not productive.
I look around at the world since WWII and fail to see this horror. I look at Wei Dai's strategy and see the horror. loqi remarked about Everett branches, but imagining the measure of the wave function where the Cold War ended with nuclear conflagration fails to convince me of anything.
This is a distinction without a difference. If H bombs D, H has lost
This assumption determines (or at least greatly alters) the debate, and you need to make a better case for it. If H really "loses" by bombing D (meaning H considers this outcome less preferable than proliferation), then H's threat is not credible, and the strategy breaks down, no exotic decision theory necessary. Looks like a crucial difference to me.
That depends on who precommits "first". [...]
This entire paragraph depends on the above assumption. If I grant you...
It's an old book, I know, and one that many of us have already read. But if you haven't, you should.
If there's anything in the world that deserves to be called a martial art of rationality, this book is the closest approximation yet. Forget rationalist Judo: this is rationalist eye-gouging, rationalist gang warfare, rationalist nuclear deterrence. Techniques that let you win, but you don't want to look in the mirror afterward.
Imagine you and I have been separately parachuted into an unknown mountainous area. We both have maps and radios, and we know our own positions, but don't know each other's positions. The task is to rendezvous. Normally we'd coordinate by radio and pick a suitable meeting point, but this time you got lucky. So lucky in fact that I want to strangle you: upon landing you discovered that your radio is broken. It can transmit but not receive.
Two days of rock-climbing and stream-crossing later, tired and dirty, I arrive at the hill where you've been sitting all this time smugly enjoying your lack of information.
And after we split the prize and cash our checks I learn that you broke the radio on purpose.
Schelling's book walks you through numerous conflict situations where an unintuitive and often self-limiting move helps you win, slowly building up to the topic of nuclear deterrence between the US and the Soviets. And it's not idle speculation either: the author worked at the White House at the dawn of the Cold War and his theories eventually found wide military application in deterrence and arms control. Here's a selection of quotes to give you a flavor: the whole book is like this, except interspersed with game theory math.
I sometimes think of game theory as being roughly divided in three parts, like Gaul. There's competitive zero-sum game theory, there's cooperative game theory, and there are games where players compete but also have some shared interest. Except this third part isn't a middle ground. It's actually better thought of as ultra-competitive game theory. Zero-sum settings are relatively harmless: you minimax and that's it. It's the variable-sum games that make you nuke your neighbour.
Sometime ago in my wild and reckless youth that hopefully isn't over yet, a certain ex-girlfriend took to harassing me with suicide threats. (So making her stay alive was presumably our common interest in this variable-sum game.) As soon as I got around to looking at the situation through Schelling goggles, it became clear that ignoring the threats just leads to escalation. The correct solution was making myself unavailable for threats. Blacklist the phone number, block the email, spend a lot of time out of home. If any messages get through, pretend I didn't receive them anyway. It worked. It felt kinda bad, but it worked.