I am fond of this kind of multiverse reasoning. One place I look for inspiration is Wolfram's book A New Kind of Science. This book can be thought of as analogous to the early naturalists' systematic exploration of the biological world, with their careful diagrams and comparisons, and attempts to identify patterns, similarities and differences that would later be the foundation for the organization system we know today. Wolfram explores the multiverse by running a wide variety of computer simulations. He is often seen as just using CA models, but this is not true - he tries a number of computational models, but finds the same basic properties in all of them.
Generally speaking, there are four kinds of universes: static, repeating, random, and chaotic. Chaotic universes combine stability with a degree of dynamism. It seems that only chaotic universes would be likely abodes of life.
The question is whether there are likely to be universes which are basically stable, with predictable dynamics, except that when certain patterns and configurations are hit, there is a change of state, and the new pattern is the seed for an explosive transition to a whole new set of patterns. And further, this seed pattern must be quite rare and never be hit naturally. Only intelligence, seeking to explore new regimes of physics, can induce such patterns to exist. And further, the intelligence does not anticipate the explosive development of the seed, they don't know the physics well enough.
From the Wolfram perspective, it seems that few possible laws of physics would have these properties, at least if we weight the universes by simplicity. A universe should have the simplest possible laws of physics that allow life to form. For these laws to incidentally have the property that some particular arrangement of matter/energy would produce explosive changes, while other similar arrangements would do nothing, would seem to require that the special arrangement be pre-encoded into the laws. That would add complexity which another universe without the special arrangement encoding would not need, hence such universes would tend to be more complex than necessary.
It's worth noting that coming up with configurations that require intelligence (or at least life) to produce isn't that hard. The only really obvious one I know of in our universe is bulk refrigeration below 2.7K, but given the simplicity of that one I strongly suspect there are others.
On the likelihood of such a state inducing a large-scale phase change, I'm in agreement. It seems implausible unless the universe is precisely tuned to allow it.
Nobel laureate Marie Curie died of aplastic anemia, the victim of radiation from the many fascinating glowing substances she had learned to isolate.
How could she have known? And the answer, as far as I can tell, is that she couldn't. The only way she could have avoided death was by being too scared of anything new to go near it. Would banning physics experiments have saved Curie from herself?
But far more cancer patients than just one person have been saved by radiation therapy. And the real cost of banning physics is not just losing that one experiment - it's losing physics. No more Industrial Revolution.
Some of us fall, and the human species carries on, and advances; our modern world is built on the backs, and sometimes the bodies, of people who took risks. My father is fond of saying that if the automobile were invented nowadays, the saddle industry would arrange to have it outlawed.
But what if the laws of physics had been different from what they are? What if Curie, by isolating and purifying the glowy stuff, had caused something akin to a fission chain reaction gone critical... which, the laws of physics being different, had ignited the atmosphere or produced a strangelet?
At the recent Global Catastrophic Risks conference, someone proposed a policy prescription which, I argued, amounted to a ban on all physics experiments involving the production of novel physical situations - as opposed to measuring existing phenomena. You can weigh a rock, but you can't purify radium, and you can't even expose the rock to X-rays unless you can show that exactly similar X-rays hit rocks all the time. So the Large Hadron Collider, which produces collisions as energetic as cosmic rays, but not exactly the same as cosmic rays, would be off the menu.
After all, whenever you do something new, even if you calculate that everything is safe, there is surely some probability of being mistaken in the calculation - right?
So the one who proposed the policy, disagreed that their policy cashed out to a blanket ban on physics experiments. And discussion is in progress, so I won't talk further about their policy argument.
But if you consider the policy of "Ban Physics", and leave aside the total political infeasibility, I think the strongest way to frame the issue - from the pro-ban viewpoint - would be as follows:
Suppose that Tegmark's Level IV Multiverse is real - that all possible mathematical objects, including all possible physical universes with all possible laws of physics, exist. (Perhaps anthropically weighted by their simplicity.)
Somewhere in Tegmark's Level IV Multiverse, then, there have undoubtedly been cases where intelligence arises somewhere in a universe with physics unlike this one - i.e., instead of a planet, life arises on a gigantic triangular plate hanging suspended in the void - and that intelligence accidentally destroys its world, perhaps its universe, in the course of a physics experiment.
Maybe they experiment with alchemy, bring together some combination of substances that were never brought together before, and catalyze a change in their atmosphere. Or maybe they manage to break their triangular plate, whose pieces fall and break other triangular plates.
So, across the whole of the Tegmark Level IV multiverse - containing all possible physical universes with all laws of physics, weighted by the laws' simplicity:
What fraction of sentient species that try to follow the policy "Ban all physics experiments involving situations with a remote possibility of being novel, until you can augment your own intelligence enough to do error-free cognition";
And what fraction of sentient species that go ahead and do physics experiments;
Survive in the long term, on average?
In the case of the human species, trying to ban chemistry would hardly have been effective - but supposing that a species actually could make a collective decision like that, it's at least not clear-cut which fraction would be larger across the whole multiverse. (We, in our universe, have already learned that you can't easily destroy the world with alchemy.)
Or an even tougher question: On average, across the multiverse, do you think you would advise an intelligent species to stop performing novel physics experiments during the interval after it figures out how to build transistors and before it builds AI?