Why do instrumentalists focus on predictions about observable phenomena?

Instrumentalists focus on predictions about observable phenomena because they view scientific theories as tools for solving practical problems rather than as literal descriptions of an underlying reality. This perspective is motivated by the belief that theories are underdetermined by empirical evidence, meaning no finite amount of data can conclusively prove a theory is true.1

Because instrumentalists doubt that theoretical terms correspond to an external reality, they argue that the value of a theory should be measured by its utility and inferential reliability—its ability to "save the phenomena"—rather than its truth or falsehood. From this viewpoint, questioning whether a theory is "true" is often considered meaningless; instead, the focus remains on whether a theory is empirically adequate, allowing scientists to generate accurate predictions from observable evidence. This approach avoids the "miraculous" assumption that theories must be true to be successful, suggesting instead that scientific success is simply the result of constructing theories that effectively capture observable truths.12