While this article claims to offer a proof of god that the author thinks persuasive, I hate to be the one to show it fails at what it aims at proving.
The argument here is
A being is said to be possible if we can conceive no contradiction in the idea of it, and impossible if we can conceive a contradiction (as we do in the idea of a square triangle, for example).
but this cannot be said to be true for
an omnipotent, omniscient, and perfectly good God