You can throw all sorts of interaction terms with unknown coefficients in there and the renormalization will pare down any inconsistent with large distance symm

You can throw all sorts of interaction terms with unknown coefficients in there and the renormalization will pare down any inconsistent with large distance symmetries. The remaining unknown coefficients are equated to combinations of known and unknown physical constants, to find the unknown ones requires a new measurement (AKA massive international experiments or cosmological observation). edit: Weinberg explains: https://www.int.washington.edu/PROGRAMS/talent13/refs/weinberg_rg_good_thing.pdf https://www.int.washington.edu/PROGRAMS/talent13/refs/weinbe...