Answer

I’m not sure I understood the question. But think about an atheist who encounters an argument that proves to him the existence of God. If the argument is logical, then what is really happening is that he discovers that he already believed in Him beforehand, only he wasn’t aware of it. For example, the physico-theological argument: the world is complex, and a complex thing does not come into being on its own. If those two premises are acceptable to you, then already now you are an implicit and unconscious believer in God.
But if I tell you that without God there is no valid and binding morality, you could logically argue that if so, then indeed there is no morality. But it is possible that suddenly you catch yourself and say that it cannot be that morality is not valid, and therefore it is clear that God really does exist. That is already a kind of rhetorical persuasion. It can also be translated into logic, and I discussed this at length in my book The First Existent, fourth conversation.