models are aspects of a mind, and existence is an aspect of a subset of a model; to ask whether a mind exists is a category error
Sort of, yes. Except mind is also a model.
So I’m not sure what an instrumentalist’s argument rejecting solipsism looks like.
Well, to a solipsist hers is the only mind that exists, to an instrumentalist, as we have agreed, the term exist does not have a useful meaning beyond measurability. For example, the near-solipsist idea of a Boltzmann brain is not an issue for an instrumentalist, since it changes nothing in their ontology. Same deal with dreams, hallucinations and simulation.
Sort of, yes. Except mind is also a model.
Well, to a solipsist hers is the only mind that exists, to an instrumentalist, as we have agreed, the term exist does not have a useful meaning beyond measurability. For example, the near-solipsist idea of a Boltzmann brain is not an issue for an instrumentalist, since it changes nothing in their ontology. Same deal with dreams, hallucinations and simulation.