It seems weird to frame arguments that "my opponents should change first" as being about reachability and not just a classic game of chicken.
In the classic game of chicken you have two players. In case of two tribes, you have many players, some of them with more complex preferences, such as: "I would prefer to live in peace, but if the war is inevitable then I would prefer my tribe to win", etc.
Saying that it's "just a classic game of chicken" is also a claim about which solutions are reachable (tribe 1 wins, or tribe 2 wins) and which are not (the peaceful members of both tribes may together find a system to keep their belligerent comrades under control).
Is reachability just a synonym for "this is complicated" then? Or is there some simple underlying dynamic that you are trying to describe other than the obvious defect/cooperate outcome matrix? "Both sides swerve" is also a potential outcome in a game of chicken.
I understood "reachability" as "according to how the problem is framed, this is a possible solution". Either because other possible solutions are not even mentioned, or because the speaker insists that they are not possible.
Like, when I give you a false dilemma, I have described a situation which has two reachable outcomes.
The first example doesn't seem like a game of chicken to me, since neither Alexi nor Beth can make a change themselves. It may be that they have "inherited" the debate from their political factions' respective allies, who are actually playing a game of chicken. But Alexi and Beth are doing the classic political topic "talking past one another" and part of this seems to be that they're treating different sets of actions as reachable, and only assigning should-ness to reachable actions.
Dennis: That won't be enough, we need to make individual changes!
...
On the other hand Dennis thinks that individual action is reachable and big government action as impossible.
Dennis seems to be more worried about speed, i.e. response times.
I appreciate this post a lot. In particular, I think it's cool that you establish a meta-frame, or at least class of frames. Also, I've had debates that definitely have had reachability mismatches in the past and I hope that that I'll be able to just link to this post in the future.
The most frequent debate mismatch I have is on a subject you mention: climate change. I generally take the stance of Clara: the way I view it, it's a coordination problem, and individual action, no matter how reachable, I model as having completely unsubstantial effect. In some sense, one could claim that all arguments should only be about the nature of actions that either individual involved in the conversation could actually take. On the other hand (and the stance I take in this scenario), communication can be used as a signal to establish consensus on the actions that others should take. I expect that this sort of mismatch could be the cause reachability mismatches in general. One participant can prioritize the personal relevance of the conversation while another could try to prioritize arguments for actions that have the most effect, whether or not anyone can actually make them happen. Another way to view this problem is "working backwards" from the problem or "working forwards" from the actions we can take.
Alexi and Beth are not Blues or Greens, but are talking about a conflict in a foreign nation between the Blues and the Greens. The Blues are the majority in both numbers and power, and have created a number of laws which restrict the cultural and religious traditions of Greens. In response, the Green minority commonly protest, a smaller number are civilly disobedient, and a tiny number have become dangerous terrorists.
Alexi: I wish the Blues would just stop oppressing the Greens. It's ridiculous the treatment that Greens have to put up with. If the Blues would repeal those ridiculous laws then they could begin to get along.
Beth: What do the Greens expect? If they keep disrupting blue society and committing terrorist acts then there's going to be retribution.
Alexi: That's absurd! Most Greens are just trying to live their lives, and those that aren't are only responding to to the awful situation they've been put in.
Beth: The Blues are being killed, they fear for their lives! If the Greens could behave better then maybe they could enter actual negotiations for better treatment.
(Yes this was a metaphor for the particular conflict you were thinking of, definitely not any of the dozens of other conflicts it could just as easily represent)
Clara and Dennis are discussing solutions to climate change.
Clara: Carbon capture or blocking out sunlight is how we can solve this, because any billionaire or government could do it!
Dennis: But that's ridiculous, we need to reduce emissions now! We've done alright with transferring centralized energy to low-carbon and renewable alternatives, the next step is to stop using cars and high-carbon materials so much.
Clara: If that's the case they need to be banned, or taxed!
Dennis: That won't be enough, we need to make individual changes! We need to change our attitudes!
These both have the same flavour.
What's going on is a question of reachability. Eliezer Yudkowsky has written about reachability and should-ness in terms of free will, with should-ness flowing backwards from desirable states of the future.
In both cases, the future state that the interlocutors want is pretty similar (Blue and Green integration and peace, less climate change), but they disagree on which actions are reachable. Instead though, this manifests as a disagreement about what "should" be done.
Alexi is seemingly taking a much more Pro-Green position, compared to Beth's. She does this by framing the Blues as subjects, whose actions are reachable; and the Greens as objects, whose actions are simply functions of the worlds. Beth does the opposite. Whether their divergent views are due to their political tribes (Orange vs Purple perhaps?) or something else entirely is not clear.
Clara sees government-centralized and unilateral actions as reachable, and changing everyone's minds as impossible. On the other hand Dennis thinks that individual action is reachable and big government action as impossible.
Establishing reachability is crucial to having sensible debates. It's a type of frame for conversation. If you're running an activist group, you might have several types of reachability frame. One for what sorts of specific campaigns you can actually do, and one for what you wish everyone, or the government, would do in an ideal world.
It could even specifically help to switch reachability frames. Discuss what should be done labelling all possible actions the government could take as reachable. Then swap to discussing what actions you can personally take to shift the governments actions towards those.
For this reason, I think the important takeaway is to notice reachability frames, and to point them out when reachability disagreements occur.