It isn’t about believing in God. I know God is CAPABLE of doing such things, so I’m not denying that it’s possible. But, even though God COULD have done it, doesn’t necessarily mean He DID.
I believe God COULD have created the Earth in 6 days if He wanted to. But I don’t believe He DID. It’s not that I think He’s not powerful enough, it’s that I recognize that for some reason or another He chose to do it another way.
I can assure you that I most certainly believe in an infinite God who is capable of everything.
There are clues which point to a story being allegorical.
1. There is no historical evidence. (Of course, this doesn’t definitively prove that it’s allegory, it might just mean we haven’t found the proof yet.)
2. The early Christians took it allegorically. (And I can point you toward many examples where early Christians took certains tories allegorically.)
3. The language used in the story is poetic language. (Like in the creation account in Genesis, the repetition of “and he saw that it was good” is poetic language, making it more likely that the author intended to write a poem or allegory instead of history.)
The Bible doesn’t just come out and say, “oh, hey, that story was just an allegory”, but that doesn’t mean we can’t understand that the story is an allegory based on biblical and historical clues.
There is always a chance that I’m wrong and an event in the Bible that I think is merely allegory may actually be literal history. But for now I’m sticking with the theory that the events in Jonah are allegorical.
I respect the idea that the events may be literal history, it’s just that I disagree.