Beginning about 1930, Arthur Holmes and Felix Andries Vening Meinesz both argued that subcrustal convection currents were inevitable because of differential radioactive heating and that these currents exerted a viscous drag on the base of the crust. Holmes and Vening Meinesz, however, were in distinct disagreement on the mechanism by which convection currents caused crustal “downbuckling” at island arcs, and more generally, the global pattern of ascending and descending convection currents. Hence it is somewhat misleading to portray them as scientific allies, as is commonly done.