The opinion article by Jones (Seism. Res. Lett. 71 , 395-396, 2000) and follow-up communications in Seismological Research Letters ( 71 , 670-672, 2000) discuss pros and cons of seismic moment vs. magnitude as scaling sizes for the earthquake source and possible related units. While the moment clearly provides a better physical quantification of the earthquake source than magnitude, it has a simple and easily fixable shortcoming that stems from the inclusion of rigidity in the definition of the moment. The basic problem is that linear elastic waves generated by a slip source have no information on material properties at the source region itself. This is because elastic properties at the source produce two opposite effects on (a) the amount of slip generated by a given force (or stress drop) and (b) the propagation of disturbances away from the source. As shown analytically in my 1989 paper (Geophys. J. Int. 98 , 213-222), these two opposite effects cancel out internally in the seismic representation theorem that formalizes the calculations of seismic radiation from a slip source. Heaton and Heaton (Bull. Seism. Soc. Am. 79 , 813-841, 1989) give related static results. While the …