Implausible premises aside, I’m not convinced this actually resolves the paradox.
The first spacefaring civilization fills the galaxy/universe with Catastrophe Engines at the maximum usable density.
But now the second spacefaring civilization doesn’t have any room to build Catastrophe Engines, so they colonize space the regular way. And we’re right back at the original problem: either life has to be rare enough that everybody has room to build Engines, or there’s lots of life out there that had to expand the non-Engine way but we somehow can’t see them.
The second civilization would just go ahead and build them anyways, since doing so maximizes their own utility function. Of course, there is an additional question of whether and how the first civilization will try to stop this from happening, since the second civ’s Catastrophe Engines reduce their own utility. If the first civ ignores them, the second civ builds Catastrophe Engines the same way as before. If the first civ enforces a ban on Catastrophe Engines, then the second civ colonizes space using conventional methods. But most likely the first civ would eliminate the second civ (the “Berserker” scenario.)
So instead of every civ fillings its galaxy, we get every civ building one in every galaxy. For this to not result in an Engine on every star, you still have to fine-tune the argument such that new civs are somehow very rare.
There are some hypotheticals where the details are largely irrelevant, and you can back up and say “there are many possibilities of this form, so the unlikeliness of my easy-to-present example isn’t the point”. “Alien civs exist, but prefer to spread out a lot” does not appear to be such a solution. As such, the requirement for fine-tuning and multiple kinds of exotic physics seem to me like sufficiently burdensome details that this makes a bad candidate.
On some level it’s fine to make the kinds of qualitative arguments you are making. However, to assess whether a given hypothesis really robust to parameters like ubiquity of civilizations, colonization speed, and alien psychology, you have to start formulating models and actually quantify the size of the parameter space which would result in a particular prediction. A while ago I wrote a tutorial on how to do this:
which covers the basics, but to incorporate alien psychology you would have formulate the relevant game-theoretic models as well.
The pitfall of the kinds of qualitative arguments you are making is that you risk confusing the fact that “I found a particular region of the parameter space where your theory doesn’t work” with the conclusion that “Your theory only works in a small region of the parameter space.” It is true that under certain conditions regarding ubiquity of civilizations, colonization speed, and alien diplomatic strategy, that Catastrophe Engines end up being built on every star. However, you go on to claim that in most of the parameter space, such an outcome occurs, and that the Fermi Paradox is only observed in a small exceptional part of the parameter space. Given my experience with this kind of modeling, I predict that Catastrophe Engines actually are robust to all but the most implausible assumptions about ubiquity of intelligent life, colonization speed, and alien psychology, but you obviously don’t need to take my word on it. On the other hand, you’d have to come up with some quantitative models to convince me of the validity of your criticisms. In any case, continuing to argue on a purely philosophical level won’t serve to resolve our disagreement.
Implausible premises aside, I’m not convinced this actually resolves the paradox.
The first spacefaring civilization fills the galaxy/universe with Catastrophe Engines at the maximum usable density.
But now the second spacefaring civilization doesn’t have any room to build Catastrophe Engines, so they colonize space the regular way. And we’re right back at the original problem: either life has to be rare enough that everybody has room to build Engines, or there’s lots of life out there that had to expand the non-Engine way but we somehow can’t see them.
The second civilization would just go ahead and build them anyways, since doing so maximizes their own utility function. Of course, there is an additional question of whether and how the first civilization will try to stop this from happening, since the second civ’s Catastrophe Engines reduce their own utility. If the first civ ignores them, the second civ builds Catastrophe Engines the same way as before. If the first civ enforces a ban on Catastrophe Engines, then the second civ colonizes space using conventional methods. But most likely the first civ would eliminate the second civ (the “Berserker” scenario.)
Then why isn’t there an Engine on every star?
The second civ would still avoid building them too close to each other. This is all clear if you do the analysis.
So instead of every civ fillings its galaxy, we get every civ building one in every galaxy. For this to not result in an Engine on every star, you still have to fine-tune the argument such that new civs are somehow very rare.
There are some hypotheticals where the details are largely irrelevant, and you can back up and say “there are many possibilities of this form, so the unlikeliness of my easy-to-present example isn’t the point”. “Alien civs exist, but prefer to spread out a lot” does not appear to be such a solution. As such, the requirement for fine-tuning and multiple kinds of exotic physics seem to me like sufficiently burdensome details that this makes a bad candidate.
EDIT: Edited my response to be more instructive.
On some level it’s fine to make the kinds of qualitative arguments you are making. However, to assess whether a given hypothesis really robust to parameters like ubiquity of civilizations, colonization speed, and alien psychology, you have to start formulating models and actually quantify the size of the parameter space which would result in a particular prediction. A while ago I wrote a tutorial on how to do this:
http://lesswrong.com/lw/5q7/colonization_models_a_tutorial_on_computational/
which covers the basics, but to incorporate alien psychology you would have formulate the relevant game-theoretic models as well.
The pitfall of the kinds of qualitative arguments you are making is that you risk confusing the fact that “I found a particular region of the parameter space where your theory doesn’t work” with the conclusion that “Your theory only works in a small region of the parameter space.” It is true that under certain conditions regarding ubiquity of civilizations, colonization speed, and alien diplomatic strategy, that Catastrophe Engines end up being built on every star. However, you go on to claim that in most of the parameter space, such an outcome occurs, and that the Fermi Paradox is only observed in a small exceptional part of the parameter space. Given my experience with this kind of modeling, I predict that Catastrophe Engines actually are robust to all but the most implausible assumptions about ubiquity of intelligent life, colonization speed, and alien psychology, but you obviously don’t need to take my word on it. On the other hand, you’d have to come up with some quantitative models to convince me of the validity of your criticisms. In any case, continuing to argue on a purely philosophical level won’t serve to resolve our disagreement.