Full Idea
Instrumentalism is so called because it regards theories not as attempts to describe or explain the world, but as instruments for making predictions; for the instrumentalist, asking about the truth of a theory is a conceptual mistake.
Gist of Idea
Instrumentalists regard theories as tools for prediction, with truth being irrelevant
Source
Alexander Bird (Philosophy of Science [1998], Ch.4)
Book Reference
Bird,Alexander: 'Philosophy of Science' [UCL Press 2000], p.125
A Reaction
It cannot be denied that theories are used to make predictions, and there is nothing wrong with being solely interested in predictions. I cannot make head or tail of the idea that truth is irrelevant. Why is a given theory so successful?