So, the First Mover cannot exist alone, a First Moved is also required to have existed for the same time.
Several points:
First from Edward Feser:
Aristotelian, Neo-Platonic, Thomistic, and Leibnizian cosmological arguments are all concerned to show that there must be an uncaused cause even if the universe has always existed. Of course, Aquinas did believe that the world had a beginning, but (as all Aquinas scholars know) that is not a claim that plays any role in his versions of the cosmological argument.
When he argues there that there must be a First Cause, he doesn’t mean “first” in the order of events extending backwards into the past. What he means is that there must be a most fundamental cause of things which keeps them in existence at every moment, whether or not the series of moments extends backwards into the past without a beginning.
Source:
Edward Feser: So you think you understand the cosmological argument?
So, if the universe has always existed, it still requires the explanatory First Cause to exist independently of the universe and to keep the universe in existence because the universe is contingent – it doesn’t exist a se or of its own accord, nor can it explain or cause its own existence. So, First Mover still required even if First Moved always existed.
Second, yours is an objection that is entirely lexical or definitional, so it proves exactly nothing.
We can grant you that it would be an infringement of definitional terms to refer to a “Creator” absent a creative act or a creation, but that doesn’t demonstrate that the Self-Existent Being (whose Essence is Existence) that we also refer to as Creator
did not,
does not, or
could not exist independently of the creation or “First Moved.”
Third,
Gorgias’ point about God as eternal Being would imply that the universe exists as a whole, perhaps even eternally, complete with a beginning → end time signature much as the world in a novel with its own internal time structure exists vis a vis the author of the novel and separate from the world the author lives within. The author doesn’t inhabit the novel, nor is his/her existence at all dependent upon the existence of the novel.
So while you technically might be correct that a novel writer (or creator) cannot properly be referred to as a “novel writer” until the novel is completed, the existence of the novel isn’t what actually makes the author a writer, since the literary talents, writing skills, creativity, etc., that the writer possesses are what make the author a “writer,” in the non-trivial and meaningful sense. It isn’t merely the existence of a novel that makes the person a writer, because even if all copies of any or all of his/her works were to suddenly go out of existence, it wouldn’t make any sense to say the novel writer, too, suddenly went out of existence with them. No, s/he still exists with all the skills required to pen another work – so still “a writer.”