In Peskin- Schroeder, pag 412: "In massless phi4 theory, the one-loop propagator correction is completely canceled by mass counterterm." So, do massless theory provides mass counterterm? How is it generated? Maybe from a bare mass...don't have any clue. I'm confused because it seems that Peskin uses such a counterterm to eliminate the propagator ultraviolet divergencies (at 1 loop) but every kind of reference in a mass counterterm disappear in the following pages. So...no clue!