As for your first question, there are certainly other thought systems (or I suppose decision theories) that allow a thing to propagate itself, but I highlight a hypothetical decision theory that would be ideal in this respect. Of course, given that things are different from each other (as you mention), this ideal decision theory would necessarily be different for each of them.
Additionally, as the ideal decision theory for self-propagation is computationally intractable to follow, “the most virulent form” isn’t[1] actually useful for anything that currently exists. Instead, we see more computationally tractable propagation-based decision theories based on messy heuristics that happened to correlate with existence in the environment where such heuristics were able to develop.
For your final question, I don’t think that this theory explains initial conditions like having several things in the universe. Other processes analogous to random mutation, allopatric speciation, and spontaneous creation (that is, to not only species, but ideas, communities, etc.) would be better suited for answering such questions. “Propagative decision theory” does have some implications for the decision theories of things that can actually follow a decision theory, as well as giving a very solid indicator on otherwise unsolvable/controversial moral quandaries (e.g. insect suffering), but it otherwise only really helps as much as evolutionary psychology when it comes to explaining properties that already exist.
Other than in the case that some highly intelligent being manages to apply this theory well enough to do things like instrumental convergence that the ideal theory would prioritize, in which case this paragraph suddenly stops applying.
As for your first question, there are certainly other thought systems (or I suppose decision theories) that allow a thing to propagate itself, but I highlight a hypothetical decision theory that would be ideal in this respect. Of course, given that things are different from each other (as you mention), this ideal decision theory would necessarily be different for each of them.
Additionally, as the ideal decision theory for self-propagation is computationally intractable to follow, “the most virulent form” isn’t[1] actually useful for anything that currently exists. Instead, we see more computationally tractable propagation-based decision theories based on messy heuristics that happened to correlate with existence in the environment where such heuristics were able to develop.
For your final question, I don’t think that this theory explains initial conditions like having several things in the universe. Other processes analogous to random mutation, allopatric speciation, and spontaneous creation (that is, to not only species, but ideas, communities, etc.) would be better suited for answering such questions. “Propagative decision theory” does have some implications for the decision theories of things that can actually follow a decision theory, as well as giving a very solid indicator on otherwise unsolvable/controversial moral quandaries (e.g. insect suffering), but it otherwise only really helps as much as evolutionary psychology when it comes to explaining properties that already exist.
Other than in the case that some highly intelligent being manages to apply this theory well enough to do things like instrumental convergence that the ideal theory would prioritize, in which case this paragraph suddenly stops applying.