  IIIp51 assures us, moreover, that the same object might affect different people, or even the same person at different times, in different ways. So Spinoza protects himself from the charge that IIIp28 is obviously false (albeit at the risk of forwarding an unfalsifiable psychological claim) by arguing that, despite the seeming simplicity of that proposition, it cannot be falsified by the great variety of conscious human motives.