 Although their account of predictivism is tailored initially to the curve-fitting problem, it is by no means limited to such cases. They note that it is natural to think of a model as analogous to the ontological framework of a scientific theory where the various ontological commitments can function as ‘adjustable parameters’—for example, the Ptolemaic and Copernican world pictures both begin with a claim that a certain entity (the sun or the earth) is at the center, and these models are articulated by producing models with adjustable parameters.