  In considering Locke’s execution of this plan in the Essay we discover a trend that grows stronger in subsequent Empiricist thinkers like Hume and his 19th and 20th century successors. One can be easily misled into thinking that there was a general agreement on both sides of this controversy about the explanandum: we can call that our understanding, or simply the intelligibility of the world. The innateness controversy would then be about which theory can provide the best explanation of this agreed-upon ‘Understanding’. But this positivistic paradigm of the dynamics of theory-selection does not fit the real debate. A Kuhnian perspective is closer to the truth. Empiricists inevitably reconfigured the explanandum – some elements of the original explanandum were to be (better) explained by the Empiricist account, but a good deal of it was to be explained away as Rationalist over-reaching. Our earlier example of Descartes’ a priori claim that matter cannot think is a case in point. Locke’s system was criticized for not being able to exclude the possibility of thinking matter. But for Locke, that possibility was not excludable, despite Descartes’ clear and distinct perception to the contrary. So Locke does not accept the explanatory burden of providing an Empiricist account of how it is that the Understanding grasps the falsity of materialism and the truth of dualism. Our knowledge of the world does not extend as far as the Rationalist thinks, and the true explanatory burden is therefore lighter than the Rationalist makes it out to be. This pattern of explaining away reaches its culmination in Hume, who sees more clearly than Locke that the fact that the mind can make the world intelligible is itself a philosophical presumption that needs to be explained away. Hume replaces it with a naturalistic account of how we track the way the world appears to us, and collate the results to guide us in the future. Our understanding of the world, in Hume’s philosophy, is thinned out into something the Rationalists would not count as Understanding at all; his conception of human reason is, appropriately enough, a pale shadow of their Reason.