 If Spinoza's principle of inertia is to provide a ground for PCP IIp17 taken as involving “conari” in an active sense, then it must be taken to amount to the claim not just that bodies will not in fact change their state unless externally determined to do so, but also that even while external causes are acting on a body (e.g., the sling holding the stone in circular motion), the body's own impulse is at work actively endeavoring to determine it to move as it would in the absence of that external cause. And reading Spinozistic inertia this way, imputing to the body a continuous effort to move so as to maintain the state it would be in absent external determination, also suits it to ground the PLMM. Given the symmetry of interaction, each of the bodies to an interaction, being externally determined to change by the other, will strive to resist change as far as it is able. Plausibly, then, the total change of state resulting from the resolution of the opposition of the interacting bodies will be the least total possible. This suggests, at least tentatively, that even in the PCP, Spinoza is at work attempting to shore up worries in the foundations of Cartesian physics that stem from the unduly passive Cartesian construal of the equation of body with extension.