The whole argument is circular, yes. It's a metaphysical problem. One can't conclusively proove anything with physical evidence. One can use the word "natural"

The whole argument is circular, yes. It's a metaphysical problem. One can't conclusively proove anything with physical evidence. One can use the word "natural" to mean "unguided", but that position is just begging the question. It assumes nature and its laws are inherently unguided. Why did virus A proliferate and not virus A'? Why did gene B mutate and not gene B`? Is that "random"? Well, we don't have evidence either way, do we? We can assume, I suppose.