But Giorgi pointed out that the volt and the rest could be "made" coherent if one gave up on the idea that all physical quantities must be expressible in terms of dimensions of length, mass, and time, and admitted a "fourth base dimension" for electric quantities. Any practical electrical unit could be chosen as the new fundamental unit, independent from the meter, kilogram, and second. Likely candidates for the fourth independed unit included the coulomb, the ampere, the volt, and the ohm, but eventually the ampere proved to be the most convenient as far as metrology. Moreover, the freedom gained by making an electric unit independent from the mechanical units could be used to rationalize Maxwell's equations.