Theoretical physicists must work hard to learn how to wield their tools; rarely do the tools of theory seem natural or obvious on their own. Once physicists learn to deploy paper tools and make calculations with them, the range of applications to which they apply the tools can widen dramatically. As with any tool, improvisation and bricolage can lead to applications that had never been envisioned by the tool's inventors. Tools such as Feynman diagrams were consistently drawn and taught as being of a piece with the reigning pictorial standards for studying particle trajectories through space...

Theoretical physicists must work hard to learn how to wield their tools; rarely do the tools of theory seem natural or obvious on their own. Once physicists learn to deploy paper tools and make calculations with them, the range of applications to which they apply the tools can widen dramatically. As with any tool, improvisation and bricolage can lead to applications that had never been envisioned by the tool's inventors. Tools such as Feynman diagrams were consistently drawn and taught as being of a piece with the reigning pictorial standards for studying particle trajectories through space and time. The resilience displayed by Feynman's diagrams in the early 1960s, when physicists such as Geoffrey Chew aimed to build a new theory from Feynman diagrams while replacing quantum field theory altogether, can be explained by the diagrams' easy assimilation into a long visual tradition for treating particles' propagation.