Pragmatism is the most distinctively American philosophical tradition. Peirce, James, and Dewey, working in the late 1800s, were suspicious of the grand metaphysical disputes European philosophers had been having for centuries. Their move: treat ideas as tools. An idea's meaning is the difference its truth would make to practice. An idea is "true" if it survives the inquiries we put it through.
This isn't relativism. Pragmatists believe in disciplined inquiry, in evidence, in being responsive to facts. What they reject is the picture of truth as a perfect correspondence between propositions and a mind-independent reality — a picture they think generates pseudo-problems. Instead: what would have to be the case for this idea to do its job? Does the idea hold up when we try?
The practical bite is enormous. William James used pragmatism to defend religious belief (if it works in your life, it earns a place). John Dewey used it to reshape education and democracy. Contemporary neo-pragmatists like Richard Rorty pushed further — denying that "truth" is a useful concept beyond what works for whom. The continuing influence is most visible in pluralist political theory, in empirical philosophy, and in the deep suspicion among American philosophers of any system claiming a god's-eye view.