Mental simulations are mental representations of possible worlds
During dreaming, planning, or imagining, we are manipulating representations of possible worlds. This challenges idealism, in that it highlights the fact that mental representations are also useful when the representandum is not an element of the real actual world, but of a virtual one. Eidetic children might have not learned yet that there’s a distinction between perception and imagination. Dreaming might be an anomalous state of confounding simulations with representations.