By humans? Do circles not exist without humans to point them out?
> According to intuitionism, mathematical objects are products of our mind, like characters in a novel. I agree, as far as it goes...
> Fictionalism holds that the mathematical universe is a collective fiction, like Star Trek or Game of Thrones.
You're right, it feels like quite a loose analogy, and only holds when discussing a "canonical" fictional universe. Still, I'm sympathetic to the idea that when we're talking about a circle we're talking about a shared abstract understanding rather than something which objectively exists.