I don't understand why one would prefer a simpler theory rather than a less simple one independent 1) aesthetic preference and/or 2) computational limitations. I am convinced that our finite powers are something we should take seriously in #theory choice (esp. since hearing a good talk by @bweatherson about this), but a friend really wants me to expect that simpler #explanations are more likely to be true than less simple ones. I can't see why that would be.
In my circles a bunch of folk support either a pure-wave interpretation of quantum physics, a broader Tegmark-style mathematical universe, etc up to full modal realism.
Given an ontology like that, it's easy to show that certain kinds of theories are true in a superset of the worlds where more specific versions of those theories are true. Example: a child psychology theory with five stages of development versus a theory with those same five stages plus one.
