I am by no means competent to criticise Descartes's Cogito, however it does puzzle me why it is felt to be so conclusive. I cannot think things into existence: that would be magic, or a divine act of creation. How, then can I think myself into existence? Surely, Descates should have said, I am, therefore I can think. Existence is, as can be seen a pre-requisite - and existence as a human to boot (or other thinking entity, such as a god, for example).
What's hard to reconcile about, "God made all that there is"? If something exists, that indicates it has a divine origin. Sure, there are contradictions - fossils don't sit well with a creation date of 23/10/4004 BC (Usher), but there are sientific anaomalies too: if you know where a subatomic particle is, you cannot know how it is moving;particles and waves are neither one thing nor the other, but have properties of both of them ... and, of course, every effect must have a cause: there is no uncaused effect. Or can science prove otherwise?
But you could say, you have to believe it happened that way, because that's what my theory holds to be true.