Why do instrumentalists emphasize accurate predictions when evaluating scientific theories?

Instrumentalists emphasize accurate predictions because they view scientific theories primarily as tools for solving practical problems rather than as literal descriptions of reality. This perspective is rooted in several key philosophical arguments:1

• Underdetermination: Instrumentalists argue that scientific theories are necessarily underdetermined by available data. Because no finite amount of empirical evidence can conclusively prove a theory is "true" or rule out all alternative explanations, they contend that the most practical criterion for evaluation is a theory's performance in generating reliable predictions.1
• Historical Skepticism: The history of science is filled with theories that were once widely accepted but later discarded (such as the ether theory). Instrumentalists argue that since even the best past theories were eventually rejected, there is no reason to assume current theories are "true" rather than simply useful for the time being.1
• Pragmatic Utility: Instrumentalism, a form of pragmatism, posits that the value of an idea lies in its usefulness. Whether a theory is "true" is considered less important than its inferential reliability and its ability to "save the phenomena"—or accurately predict observable facts.12