Positive Possibility and Representation in Modeling

Apparently modally laden terms and relations figure in scientific models, especially though not only possibility. There is an old empiricist tension between measurements as returning actual values, and stronger forms of modality. How could we measure what didn't happen, or use measurement to distinguish what didn't happen but could have, from that which did not happen and could not have? I offer several pragmatist points in the context of modeling and possibility specifically, by which to see this tension as a fruitful one. Peirce offers a view of positive possibility, where it prior to and required for actuality, and which can be differentiated from merely in-principle possibility. He also offers a view of doubt where it requires one suspend use of a belief and initiate an inquiry; views of possibility like those in Humean accounts, even pragmatic Humean views, are offering what amounts to a doubt about models that do not represent these, and only represent positive possibilities. This leads to a distinction by Price between e-representation and i-representation, where some representation is constrained externally by the environment, and some constrained internally by inferential connections. Putting these together provides a better way to understand how models can represent modality such as positive possibility, and how models can be used in ways that settle direction of fit.