 There are two noteworthy points about this explication of inertia. First, it shows that Newton recognized properties that were commonly regarded as distinct (e.g. in the Leibnizian distinction between passive and active) as merely frame-dependent representations of the same fundamental property. That is, they represent the same invariant quantity seen from different points of view. The principle that a body exerts this force “only in a change of its state” decisively separates Newton’s new view from the older notion of a specific power that is required to maintain a body in motion. This change has been noted by modern commentators (see Herivel 1965, p. 26; see also DiSalle 2013, p. 453; Disalle 2017, in Other Internet Resources). But it was already noted in Newton’s own time by George Berkeley, who emphasized the contrast between Newton’s conception and that of Leibniz: