Frank Kogan

(take two)

but the brain's interpretation of the Necker Cube's conflicting perspective is paradigmatic

Yes! But this applies every bit as much to the open cube made of sticks, if that cube made of sticks is being used as a model - i.e., if it is being used as a representation of something else or a prototype that can be used to create something else. Which is to say, if you point to the cube made of sticks and say, "Use that as a model," with no elaboration, the person you're instructing will either have to already know what you mean, on the basis of past interaction with you or on the basis of the standard practice among her and your social set or her and your profession of what cubes of sticks are models for and how to apply them, or she will have to make an educated guess or a wild guess. How to use a model isn't written into the model's physical features. And even if the person you're talking to is a structural engineer and she knows that the cube of sticks is part of a scale model of some structure she's supposed to build - say the cube is to be a structure on the front lawn of The Institute - what materials to use and how to construct them for an object that's 20 feet by 20 feet rather than 3 inches by 3 inches is something she'll only know from training and experience.

I think you're creating an unnecessary problem for yourself in your distinction between "internal" and "external." Are social practices internal or external? - my point here being that using something as a model is almost always a social practice, the result of specific training with that particular model or something like it, or a skill you've picked up in the course of your life. It's a matter of culture, and I don't think it's useful to worry about whether culture is internal or external. It starts external, when you're a baby, but you have to internalize it; but you haven't successfully internalized it if you can't recreate it in your observable behavior, in the world.

(Even if, let's say, you're the first person to model your derivation of your law of physics on someone's derivation of his law of physics, this comes from your experience of doing derivations and of your knowledge of yet other people modeling their derivations on someone else's derivations, etc.)