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Vladimir_Nesov comments on Notion of Preference in Ambient Control - Less Wrong
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Okay, I'm convinced. In case it helps someone else, here is how I now understand your argument.
We have an agent written in some program. Because the agent is a computer program, and because our 1st-order logic can handle recursion, we can write down a wff [w(x)], with one free variable x, such that, for any action-constant X, [w(X)] is a theorem if and only if the agent does v(X).
[ETA: Vladimir points out that it isn't handling recursion alone that suffices. Nonetheless, a theory like PA or ZFC is apparently powerful enough to do this. I don't yet understand the details of how this works, but it certainly seems very plausible to me.]
In particular, if the agent goes through a sequence of operations that conclude with the agent doing v(X), then that sequence of operations can be converted systematically into a proof of [w(X)]. Conversely, if [w(X)] is a theorem, then it has a proof that can be reinterpreted as the sequence of operations that the agent will carry out, and which will conclude with the agent doing v(X).
The wff [w(x)] also has the property that, given two constant U and V, [w(U) & w(V)] entails [U = V].
Now, the agent's axiom system includes [w(A)], where A is a constant symbol. Thus, if the agent does v(X), then [w(A)] and [w(X)] are both theorems, so we must have that [A=X] is a theorem.
This works (although "because our 1st-order logic can handle recursion" is not it, etc.). (Note that "[w(X)] is a theorem of T if and only if X is as we need" is weak T-representability, while I cited the strong kind, that also guarantees [~w(X)] being a theorem if X is not as we need.)
That was there because of this line from your post: "The theory should provide sufficient tools to define recursive functions and/or other necessary concepts."
Doesn't make it an explanatory sufficient condition to conclude what you did: I object to your use of "because".
Okay, thanks. My understanding is definitely vaguest at the point where the agent's program is converted into the wff [w(x)]. Still, the argument is at the point of seeming very plausible to me.
No worries. Your logic seems rusty though, so if you want to build something in this direction, you should probably reread a good textbook.
Not so much rusty as never pursued beyond the basics. The logic I know is mostly from popular books like Gödel, Escher, Bach, plus a philosophy course on modal logic, where I learned the basic concepts used to talk about interpretations of theories.