2. Anything logically possible is either actual or potential.
3. A potential Uncaused Producer can only be caused (i.e., is not 'uncaused').
4. Hence, no Uncaused Producer is merely potential.
5. Therefore, an Uncaused Producer is actual.
6. This actual Uncaused Producer we call God.
7. Therefore, God actually exists.
(cf. James F. Ross, Philosophical Theology, pp.** [When I get home and have time, I will polish this up to fit exactly what Ross wrote, but for now I'm going from memory.)