Here is a thought. Suppose that I know that if I cause A, then either B or C will eventuate. Suppose that each of B and C furthers my plan, and neither of them furthers it better than the other. Then it does not seem that sovereignty would require me to know or decide prior to my decision to cause A which of B and C would eventuate. Sovereignty perhaps requires that nothing happens that is contrary to God's plan, but it does not require that God's plan should determine every detail.
Here is second try at a notion of sovereignty built on this:
- x sovereignly executes plan P iff if we let Q be what x strongly and knowingly actualizes in executing P, and we let K be all that x knows explanatorily prior to x's decision to strongly actualize Q, and we let W be the set of all worlds at which both Q and K hold, then no world in W better fits the goals of P than any other.
In other words, x is sovereign in the execution of a plan provided that, given what x does and knows, he can't be disappointed in respect of the quality of the plan's execution.
One way to ensure sovereignty in the execution of a plan is to strongly and knowingly actualize every little detail. This is a Calvinist or Thomistic way. Another way is to know exactly how the details would turn out. That's a Molinist way. Another way is the "chessmaster way" (not my terminology or original idea; I think the view has been developed by W. Matthews Grant and Sarah Coakley): to choose a plan in such a way that no matter how things turn out, the goal wouldn't be any the less well achieved. One can do this in two ways: setting one's goal appropriately (so that whatever turns out, fits—that's not how chessmasters do it) or choosing the plan very carefully. Or a combination.
