Tesla conceives humanity as a mass urged on by a force. Though this movement does not imply change of place in the ordinary sense, the general laws of mechanical movement are applicable to it. Human energy can be measured by half the product of humanity's mass multiplied by the square of a certain hypothetical velocity. The mass is impelled in one direction by a driving force, while being resisted by a retarding force acting in the opposite direction. The difference between these forces is the effective force imparting velocity to humanity.