I used to think there was a true dichotomy between things in the physical world and things that were abstract or imagined. But now I can't seem to understand why I ever thought that way.
I consider the mental to be a subset of the physical world (just as trout are a subset of fish). All ideas, abstractions, imaginings, etc. need a physical medium - whether that be a piece of paper, a computer screen, a hard drive, or a brain. This OP is "mental" but we all understand it exists in the physical world. It's not like they're two independent things.
We all know that an imagined horse is not anything like a real horse. But just because they're vastly different (one being a large creature, the other being a specific brain state) doesn't mean they don't both exist in the physical world.
Anyone have any thoughts or refinements on this?