Yes, you're right. And seeing as there is no way of ever finding out what 'infinite' means to Descartes or indeed to anyone other than ourselves, the argument is rendered moot. But, then, is there any point in debating anything at all, because, you and I for example, could be debating whether or not spinach is good for children, however, how can I be certain that your idea of 'spinach', 'good' and even 'children' is the same as mine?
Insofar as it is restricted to a common language game? As in, it has been arrived at by common consensus. But yes, as a whole, debating anything is theoretically pointless. Welcome to the only game in town. Nietzsche is superb jouissance.
Of the three of those examples, however, only one is 'metaphysical' but the concept for all three exists in the mind. Also, please elaborate re: Ghazzali. Who was he?
Ghazzali is the theologian credited with the decline of science and philosophy in the islamic world. He essentially argued that reason leads to agnosticism and doubt, denied causality of temporal bodies, that kind of thing. see:
http://www.councilofexmuslims.com/index.php?topic=24337.0