Note that since our agent is considering possible world-programs, these world-programs are in some sense already part of the agent's program (and the agent is in turn part of some of these world-programs-inside-the-agent, which reflects recursive character of the definition of the agent-program). The agent is a much better top-level program to consider than all-possible-world-programs, which is even more of a simplification if these world-programs somehow "exist at the same time". When the (prior) definition of the world is seen as already part of the agent, a lot of the ontological confusion goes away.