I have been reading some papers from G.F. Chew and S. C. Frautschi and they do not even bother to introduce the concept of "Field" when they describe hadron interactions. My impression is that they do not need to because interactions seem to be described by single Regge-trajectories. However Gribov introduced by the end of the 1960s the "Reggeon Field Theory". When is it mandatory to introduce fields in the theory of complex angular momenta-Regge theory? Is it when Reggeons (Pomerons) interact among themselves? Do these fields verify "locality" and "causality"? I apologyze for asking, again, about this subject. I'm trying to make sense of the papers and books that I have to figure out what I need to study.