Whenever we say that "a different action could actually be instantiated" we are logically implying circumstances that are different from what they were. So, the statement becomes nonsensical if taken literally. Taken literally it turns out like this, "a different action could actually be instantiated under the same circumstances under different circumstances".
So when you say "different actions
could actually be instantiated
given the same circumstances" what do you mean by "
given the same circumstances"? This isn't making sense.
The "same circumstances" is referring to the broader event of causal necessity, within which the more specific event of choosing was happening. In the restaurant example, within the choosing event itself, it was logically necessary that "I can choose the steak" and "I can choose the salad" were both true, thus insuring that "I could have chosen the steak" would be true after I decided to order the salad.
The "broader" same circumstances can be seen in the thought experiment of "turning back the clock". We once again return to the beginning of the choosing operation in which "I can choose the salad" and "I can choose the steak" are once again true, resulting in "I could have chosen the steak" being true. So, "I could have chosen the steak" is once again true under the exact same circumstances.
However, the statement "I could have chosen the steak" itself is implying that circumstances would have to be different in order for "I would have chosen the steak" to be true.
I take issue with this:
Whenever we say that "a different action could actually be instantiated" we are logically implying circumstances that are different from what they were.
I agree that when we say we could have done otherwise we're implying "circumstances that are different from what they were".
However in philosophical discussions about free will, when incompatibilists talk about "could have done otherwise" (also known as PAP - the principal of alternative possibilities) they most definitely are
not implying "circumstances that are different from what they were".
Failure to make this distinction clear when arguing the compatibilist case will cause confusion.
Two things: First, the PAP is satisfied by the logical fact that there are always alternative possibilities, due to the very nature of the notion of a "possibility". A possibility is something that may or may not happen. If it never happens, it remains a real possibility. The fact that it never happens does not convert it to an impossibility. It simply remains something that could have happened, but never did.
A possibility exists solely within the imagination. We cannot drive a car across the possibility of a bridge. We can only drive across an actual bridge. However, a possibility serves a real function, in that we cannot build an actual bridge without first imagining a possible bridge.
A real possibility is something that we can make real if we choose to do so. Once we've determined that it is a real possibility, the fact that we never choose to actualize it does not make it impossible. It remains an actual possibility that we simply did not choose.
Second: I agree with you that it is very difficult to shake off the figurative use of "could" in "could not have been different under the same circumstances". I find myself having to recognize and make the appropriate word change after the fact, by changing "could" to "would" (or "can" to "will').
Figuratively, we have gotten into the habit of saying "could" in place of "would", because of our tendency to think that "because it would never happen, it is AS IF it could never happen". Or, "because it will not happen, it is AS IF it cannot happen". But, like all figurative statements, they are literally false.
But in reality, "I chose the salad for dinner, even though I could have ordered the steak", is considered to be true in both its parts, and not a contradiction.
Whenever choosing happens, there will always be, by logical necessity (they are required by the operation itself) at least two real possibilities to choose from, and, by logical necessity, we will be able to choose either one. This remains true even while it is causally necessary that one of these possibilities will necessarily become the single inevitable thing that we
will choose, and the other possibilities will become the inevitable other things that we
could have chosen, but didn't.