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7. Locke’s Account of Sensitive Knowledge
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7 Locke’s Account of Sensitive Knowledge George Pappas Locke’s epistemology, particularly as it concerns sensitive knowledge of external physical objects, is usually thought to suffer from both internal, textually supported difficulties, and also from powerful philosophical objections. The former difficulties concern Locke’s apparent commitment, in Book IV of the Essay, to the thesis that all sensitive knowledge is inferential , and that a crucial step in any such inference will be a premise asserting a resemblance or conformity between currently experienced ideas and features of the object. Locke seems to assert that these inferences succeed only if one knows this premise with certainty. We are never in a position to have certain knowledge of that premise, according to Berkeley and a host of later writers, and so Locke is in the unfortunate position of having committed himself to an epistemological position that he lacks the resources to sustain. There is also a philosophical objection to Locke’s account of sensitive knowledge. The idea here is that Lockean sensitive knowledge must be inferential even if Locke’s texts do not outright assert the view that these inferences move through a known-resemblance premise. Locke accepts an indirect realist account of perception, it is usually supposed, and it allows only for inferential knowledge of external bodies. Such knowledge would require a form of inductive inference that, so the argument goes, just does not work. So, independently of whether the texts actually show that Locke adopts this inferential account of sensitive knowledge, he is stuck with such an account and it ultimately fails. Locke may say that he thinks that there is sensitive knowledge, and even say that it is acquired without dependence on inference; but his theory of perception dictates otherwise and, indeed, leads directly to skepticism with regard to external objects. In this essay, I look again at this twofold picture of Locke’s epistemology which, I agree, makes Locke’s theory of knowledge look quite unappealing. On the textual side, I try to show that Locke does not adopt the inferential picture about sensitive knowledge, both because the passages in which he is said to adopt that stance do not support that reading and also because other passages point in a different direction. I also try to show, on the philosophical side, that Locke’s specific form of indirect realist theory is perfectly compatible with there being non-inferential sensitive knowledge. Sensitive Knowledge in the Essay At the outset I want to mention a number of interpretive problems that I will set aside. The first is what I call the ‘‘problem of the official definition,’’ which seems to rule out sensitive knowledge from the start. Locke says that knowledge is perception of the agreement or disagreement of relations between ideas (IV, I, 1),1 and this definition certainly seems to have the double consequence that all knowledge is between pairs or multiples of ideas, and that knowledge is had only of ideas and never of objects. The first consequence would rule out even knowledge of single, currently experienced ideas, along with knowledge of oneself; and the latter would rule out sensitive knowledge altogether. I will here assume that this problem can be solved and in a way that blocks both of these unwanted consequences.2 A second problem concerns certainty and the close tie this concept has, for Locke, to that of knowledge. Locke definitely seems to hold that all knowledge, and thus all sensitive knowledge, is also certain knowledge. Sensitive knowledge, if there is any, is surely not certain to the degree or in the manner of intuitive and demonstrative knowledge, so Locke would need a weaker concept of certainty to apply to sensitive knowledge. But it is hard to see what this might be, other than high probability—and that, Locke emphatically asserts, falls short of knowledge. I will take no stand on this issue but will set it to the side, thus tacitly assuming that Locke can provide for a concept of certainty that is stronger than high probability and still suitable for sensitive knowledge. A third problem concerns the content of propositions sensitively known. Locke not only restricts sensitive knowledge to objects ‘‘presently perceived ,’’ but also seems to restrict sensitive knowledge to propositions expressed by sentences such as ‘‘Some object or other is causing my current ideas of sensation.’’ This ‘‘restricted content problem,’’ as we might call it, excludes simple propositions such as that expressed by ‘‘There is a spherical object before me,’’ as...