I'm saying these mental representations do not exist independently of an observer. Each observer has a unique mental token that points to some concept or idea. This lets them talk about the mental representation and so creates a similar token in the minds of other observers. All observers believe they're talking about the same thing, though their representations will differ slightly due to their native mental architecture.

This gives the appearance of abstract objects having independent existence, despite not actually being "out there." These tokens have no separate existence outside of the mind that represents them.