"In, the term \"bootstrap model\" is used for a class of theories that use very general consistency criteria to determine the form of a quantum theory from some assumptions on the spectrum of particles. It is a form of S-matrix theory.In the 1960s and '70s, the ever-growing list of strongly interacting particles \u2014 mesons and baryons \u2014 made it clear to physicists that none of these particles are elementary."@en .