I guess I’d find it difficult to challenge St. Carl Sagan, but I always understood his definition of the cosmos to be “all that there is including what we know and what we don’t know.” That means, of course, for theists, the cosmos includes God. My quibble with Sagan would then be just that — his definition must include God. You might respond by saying not if God doesn’t exist. Ah, but the Many Worlds Interpretation says that everything that can happen does happen. And as Paul Davies pointed out, that proves God’s existence! (since I don’t believe in the Many Worlds, it doesn’t fly in my book.)