So, why does a specific temperature lead us to a temperature of 100 degrees, while a certain floor doesn't lead us to a fifth floor?
Or, what am I missing?
I feel I'm failing dismally to explain this. I'll try one last approach, using your 'floor' analogy.
Let's leave naturalness aside completely for a moment and compare these two sentences:
He's on the fifth floor.
He's on a fifth floor.
What does the
second sentence mean? Well, it can mean either of the following:
a) The building that he is in has
more than one fifth floor, and he's on one of those fifth floors.
b) The building that he is in has
only one fifth floor. This particular fifth floor is just one instantiation of many possible instantiations of fifth floors.
It seems to me that you are stuck in interpretation a), which obviously doesn't make a lot of sense. In fact, to go further, to you it makes
no sense at all because in your 'floor' model, it is not possible for a building to have multiple fifth floors.
This should then lead you to adopt interpretation b), which is what I've been trying to suggest. Using the 'floor' analogy, we can imagine that the world consists of multiple buildings, all with fifth floors, and he's on one of them.
I really don't think I can put it any clearer than that.