I think you could just as well have said "I believe our ideas are often formed on paper, when we write therm down. And that writing is part of the physical world. So I think the schism you presented would be void."
Sure I could've said, writing is physical. I just did, in another comment.
I think I can avoid the whole issue by observing that I can imagine things that do not physically exist, and they are not made to physically exist by dint of a conceptual representation of them physically existing in my brain.
No, because you can't ask for it's existence, before you thought of it.
>exists even when no-one is currently thinking of it
Again, who cares, it's by definition undefined, null, niente, the inbetween state of a ternary logic.
>I can imagine things
You can't will a pot of gold into existence by mere imagination, but you can't imagine an idea without it's inherint structure being real.
I'll admit, that's a simplistic outlook, but I wasn't encouraging a complicated discusion.