1. A pragmatic theory that ideas are instruments that function as guides of action, their validity being determined by the success of the action.
2. A doctrine in which ideas are instruments of action and that their usefulness determines their truth.
3. The belief that theories are useful tools for making predictions; however, they cannot be literally true or false.
4. The view that concepts are merely useful instruments, properly evaluated not as true or false, but as effective or ineffective.

A philosophy advanced by John Dewey stating that what is most important in a thing or idea is its value as a tool of action and that the truth of an idea exists in its usefulness.

Dewey favored instrumentalism over pragmatism to label the philosophy on which his views of education were based; that is, indicating that ideas are conceived as instruments for transforming the uneasiness arising from facing a problem into the satisfaction of solving it.