Principle of equivalence for all strongly interacting particles within the S-matrix framework

The notion, inherent in Lagrangian field theory, that certain particles are fundamental while others are complex, is becoming less and less palatable for baryons and mesons as the number of candidates for elementary status continues to increase. Sakata has proposed that only the neutron, proton, and A are elementary,(1) but this choice is rather arbitrary, and strong-interaction consequences of the Sakata model merely reflect the established symmetries.