Maverick repeats his circularity argument, which boils down to this:
(*) If concept F is instantiated, then it is instantiated by an individual that exists.
He has still not replied to my detailed critique of his argument, however. My critique, in brief, was that not every sentence of the form of (*) contains a circularity. For example "If a man is a bachelor then he is a bachelor who is unmarried".
I gave another objection here, which he has also clearly ignored. The objection is that if the word 'exists' on the right hand side of this definition
Some philosopher is American = An American philosopher exists
is merely a copula, then we cannot 'descend to singulars' via 'American philosopher' but only via the subject of the left hand side, namely 'philosopher'. Maverick may object that 'exist' is not a copula, in which case I accept his argument – but that does not appear to be his argument.