Is Sensitive Knowledge 'Knowledge'? Forthcoming in Locke Studies, issue 13 (2013) Nathan Rockwood, UCSD §1 Two Views on Sensitive Knowledge Locke thinks that sense perception can give us justified beliefs about the existence of material objects. Since these justified beliefs come from sense perception, Locke calls it "sensitive knowledge". Now, given its name, it might seem obvious that Locke takes sensitive knowledge to be a kind of knowledge. However, Samuel Rickless has made a surprisingly strong case that sensitive knowledge "is not, strictly speaking, a kind of knowledge" (Rickless 2008, p. 93, my emphasis).1 He gives some compelling reasons for thinking that sensitive knowledge is instead an "assurance", a kind of probable judgment that falls short of certain knowledge. Rickless's interpretation is surprising, provocative, well defended, and has garnered the interest of other Locke scholars.2 But, I will argue, it is wrong. When Locke calls sensitive knowledge "sensitive knowledge", it is because he thinks it is a kind of knowledge. I will argue that Locke takes sensitive knowledge to be certain, which means that sensitive knowledge is a genuine kind of knowledge. Further, Locke defines knowledge as the perception of a relation between ideas, and I will argue that sensitive knowledge is the perception of a relation between ideas. Since sensitive knowledge is certain, it meets the definition of knowledge, and Locke calls it knowledge, I conclude that sensitive knowledge is genuine knowledge. (What the thesis lacks for in originality it makes up for in truth.) 1 Others have made similar claims in passing, but Rickless is the first to give a strong defense of this interpretation. For example, in his influential book, Locke's Theory of Knowledge and its Historical Relations, James Gibson writes: "Locke does not claim that the conviction of external existence which is thus obtained satisfies, to the full, the theoretical requirements of knowledge" (Gibson 1960, pp. 174). More recently, Silvio Seno Chibeni claims that "Locke acknowledges that we do not strictly know the existence of bodies" (Chibeni 2005, p. 23). 2 Owen 2008; Allen 2013; Nagel, forthcoming; Rickless helpfully labels the two views at issue the Knowledge View and the Assurance View (Rickless, forthcoming). The Knowledge View maintains that sensitive knowledge is genuine knowledge. The Assurance View maintains that sensitive knowledge is highly probable judgment which Locke calls an "assurance" (E IV.xvi.6, 662). In this essay I will first explain Rickless's arguments for the Assurance View, and then I will argue that none of these arguments are ultimately persuasive. Finally, I will make a positive case for the Knowledge View. §2 The Case For the Assurance View The best textual support that Rickless provides for the Assurance View comes from the following passage: The notice we have by our senses of the existing of things without us, though it be not altogether so certain as our intuitive knowledge, or the deductions of our reason employed about the clear abstract ideas of our own minds; yet it is an assurance that deserves the name of knowledge. (E IV.xi.3, 631, my emphasis) Rickless develops three lines of argument from this passage. First, sensitive knowledge is "not altogether so certain" as intuitive and demonstrative knowledge. And if sensitive knowledge is not certain, then it is not knowledge. Second, Locke describes sensitive knowledge as an "assurance" and, Rickless argues, "Locke uses the term 'assurance' in a very specific, technical sense" to mean a highly probable judgement (Rickless 2008, p. 92). Highly probable judgments fall short of certainty, and so Locke's calling sensitive knowledge an assurance indicates that it is meant to be only a highly probable judgement rather than certain knowledge. Third, Locke says sensitive knowledge merely "deserves the name knowledge", which may imply that sensitive knowledge is called "sensitive knowledge" even though it is not actually knowledge. I will take up each of these arguments. Nathan Rockwood 2 Rickless argues that sensitive knowledge is not certain, and so cannot be knowledge (Rickless, forthcoming). Locke says that sensitive knowledge is "not altogether so certain" as intuitive or demonstrative knowledge (E IV.xi.3, 631), nor does sensitive knowledge reach "either of the foregoing degrees of certainty" (E IV.ii.14, 537). So sensitive knowledge is less certain than intuitive and demonstrative knowledge. Further, Locke defends sensitive knowledge on practical grounds that fall short of theoretical certainty. In reply to the persistent skeptic who insists that all perception might be a dream, Locke concedes that sensitive knowledge is not "free from all doubt and scruple" (E IV.xi.8, 634). So sensitive knowledge does not seem to be completely certain. Instead, Locke defends sensitive knowledge by appealing to practical considerations: we have as much certainty "as our frame can attain to" and as much as "our condition needs" for practical purposes (E IV.xi.8, 634). He makes a similar defense of sensitive knowledge elsewhere, arguing that "no man requires greater certainty to govern his actions by" than sensitive knowledge (E IV.xi.8, 634-635, my emphasis). All this suggests that Locke takes sensitive knowledge to be practically certain (i.e. certain enough for our practical purposes) but not theoretically certain. If sensitive knowledge is not completely certain (but is instead merely certain enough for our practical purposes), then it is not knowledge. Locke says that "to know and be certain, is the same thing" (Stillingfleet, W4: 145), and that "all along in my Essay I use certainty for knowledge" (Stillingfleet, W4: 273). So if Rickless is right that sensitive knowledge is a probabilistic judgment that falls short of certainty, then sensitive knowledge cannot be genuine knowledge. For "the highest probability amounts not to certainty; without which there can be no true knowledge" (E IV.iii.14, 546). Nathan Rockwood 3 The suggestion that sensitive knowledge is not completely certain, but it is certain enough for our practical purposes, leads nicely into Rickless's second argument for the Assurance View. Rickless takes "assurance" to be a technical term referring to highly probable judgment that is indistinguishable from knowledge in its practical effects (Rickless 2008, pp. 92-93). Locke says, These probabilities rise so near to certainty, that they govern our thoughts as absolutely, and influence all our actions as fully, as the most evident demonstration; and in what concerns us we make little or no difference between them and certain knowledge. Our belief, thus grounded, rises to assurance. (E IV.xvi.6, 662, my emphasis) Some highly probable beliefs are "near to certainty", but they fall short of certain knowledge. Yet these beliefs are so likely to be true that, from a practical point of view, it makes no difference whether it is certain knowledge or not. For example, Rickless would argue, even though my highly justified belief in external objects is not certain knowledge, it is so likely to be true that I am going to act as if I were certain that external objects exist. Wether it is certain or merely highly probable that external objects makes no difference in how I act. Rickless takes "assurance" to be a technical term referring to these highly probable beliefs where the practical effects are indistinguishable from knowledge. Rickless's argument that sensitive knowledge is an assurance (in the technical sense) is perhaps the strongest argument in favor of the Assurance View. For while conceding that sensitive knowledge is "not altogether so certain" as intuitive and demonstrative knowledge, Locke says that sensitive knowledge is "an assurance that deserves the name knowledge" (E IV.xi.3, 631, my emphasis). He goes on to say in the same section that "I think God has given me assurance enough of the existence of things without me", and that sensitive knowledge is "the greatest assurance we are capable of concerning the existence of material beings" (E IV.xi.3, 631, my emphasis). Elsewhere he repeatedly describes sensitive knowledge as an assurance.3 Nathan Rockwood 4 3 cf. E IV.ii.14, 536-537; IV.xi.2, 631; IV.xi.8, 634-635; IV.xi.11, 636. Since sensitive knowledge is less certain that intuitive and demonstrative knowledge, and Locke describes it as an assurance, which is a highly probable judgment (but not certain), this suggests that Locke takes sensitive knowledge to be highly probable judgment and not certain knowledge. Rickless's third line of argument is that Locke applies the honorific title "knowledge" to sensitive knowledge merely because its practical effects are indistinguishable from genuine knowledge. Sensitive knowledge is merely an assurance, yet Locke still has a reason to call it "knowledge" because sensitive knowledge is practically indistinguishable from certain knowledge (Rickless 2008, pp. 93, 98). Further, at several points Locke stops short of saying that sensitive knowledge is knowledge. Instead, he merely says that it is "an assurance that deserves the name knowledge" (E IV.xi.3, 631, my emphasis). Similarly, he says that sensitive knowledge "passes under the name of knowledge" (E IV.ii.14, 537, my emphasis). Rickless argues that "to pass under" most likely means "to be taken for...with the implication of being something else" (Rickless 2008, p. 95; cf. Oxford English Dictionary, "to pass for", definition (5a)). So saying that sensitive knowledge "deserves" and "passes under" implies that sensitive knowledge is called knowledge even though it is not actually knowledge. Rickless concludes that sensitive knowledge is not certain knowledge. Sensitive knowledge is less certain than genuine knowledge; Locke repeatedly describes it as an assurance, which is merely a highly probable belief; and Locke seems to imply that sensitive knowledge deserves to be called knowledge even though it is not actually knowledge. All this suggests that sensitive knowledge is an assurance, and not genuine knowledge. §3 The Case Against the Assurance View Nathan Rockwood 5 Although Rickless finds some initially compelling text to support the Assurance View, in this section I will argue that all three textual arguments are ultimately unconvincing. Rickless argues that the phrase "x passes under F" implies that x is not F, and since Locke says sensitive knowledge "passes under the name of knowledge" we should think that sensitive knowledge is not actually knowledge (Rickless 2008, p. 95; Rickless, forthcoming). However, Locke sometimes uses the phrase "x passes for F" when x actually is F.4 For example, Locke explains, "if the point of the sword first enter the body, it passes for a distinct species [of action], where it has a distinct name, as in England, in whose language it is called stabbing" (E III.v.11, 435, my emphasis). Pushing a sword into another's body "passes for" stabbing, and it really is stabbing. There are other examples.5 Since Locke sometimes uses the phrase "x passes for F" when x actually is F, it is reasonable to think that Locke says sensitive knowledge "passes under the name of knowledge" because it really is knowledge. Likewise, Locke might say that sensitive knowledge "deserves the name of knowledge" because it is knowledge (cf. Allen 2013, p. 251). So Locke's saying that sensitive knowledge "deserves" and "passes under" the name of knowledge does not provide much textual support for the Assurance View. The strongest argument for the Assurance View, in my mind, is Rickless's argument that "assurance" is a technical term for highly probable judgement that is indistinguishable from certain knowledge in its practical effects. However, Locke's use of "assurance" is not as restrictive as Rickless originally had supposed. David Owen points out that assurance applies to Nathan Rockwood 6 4 Rickless notes that "passes under" is a stylistic variant of the more common "passes for" (Rickless, forthcoming), so any argument about what "passes for" means will ipso facto apply to "passes under". 5 There are other examples. The passive power of iron to be drawn by loadstone passes for an inherent quality, and it really is an inherent quality (E II.xxiii.7, 299). Locke quotes a passage where Prince Maurice "passed for a very honest and pious man", and Locke affirms that the author thinks the Prince really is honest and pious (E II.xxvii.8, 334). Parrots who could talk and answer questions would "have passed for a race of rational animals", and Locke thinks they really would be rational animals; however, they would not pass for men (E II.xxvii.8, 335). Similarly, if Baalam's ass (i.e. a donkey in the Bible who miraculously talks to his master) talked its whole life, although it would be a rational animal, "it would hardly pass for a man, how much soever it were animal rationale" (E III.vi.29, 456). These last two examples show that the phrase "x pass for F" can sometimes require x to be an F. both certain knowledge and to probable judgment (Owen 2008, part 3).6 Locke says, for example, that a "full assurance...always accompan[ies] that which I call intuitive [knowledge]" (E IV.ii.6, 533, my emphasis). Also, Locke thinks "every one's certain knowledge assures him of, beyond the liberty of doubting, viz. that he is something that actually exists" (E IV.x.2, 618, my emphasis). These passages show that we can be certain and assured of the very same truths, or as Locke put it at one point, we can be "certainly assured" of "certain and undoubted knowledge" (E IV.vi.10, 584, my emphasis). Pointing out that sensitive knowledge is described as an "assurance", then, does not undermine its claim to be certain knowledge. In a more recent paper, Rickless concedes that there is a non-technical sense of assurance, but he insists that Locke is using "assurance" as a technical term when describing sensitive knowledge (Rickless, forthcoming). Assurance in the technical sense is a belief which, though not certain, is so likely to be true that we can act as if it were certain knowledge. Locke seems to be making this very claim in behalf of sensitive knowledge: he argues that sense perception is "assurance enough" for me to "produce in myself both pleasure and pain, which is one great concernment of this present state" (E IV.xi.3, 631). Since sensitive knowledge is good enough for our practical purposes, Locke may be suggesting that sensitive knowledge is an assurance rather than knowledge. It should be pointed out, though, that certain knowledge is also good enough for our practical purposes. The advantage of having an assurance is that we can act as if it were certain knowledge. Yet acting as if a claim were certain knowledge is advantageous only because acting on certain knowledge is advantageous (otherwise it would not be advantageous for us to act as if a highly probable belief were certain knowledge). Locke identifies, for example, God's existence Nathan Rockwood 7 6 Owen cites E IV.i.9, 528, and E IV.ii.6, 533. and morality (i.e. divine commands) as the "great concernments" of this life (E I.i.5, 45), presumably because God is going to eternally reward us for following his commands or eternally punish us for disobeying those commands (E II.xxviii.8, 352). For this reason acquiring certain knowledge of God's existence and of morality is one of the most practically useful things we can do. Since some knowledge is practically useful, yet still certain knowledge, Locke can appeal to the practical benefits of sensitive knowledge without undermining its status as knowledge. Moreover, certain knowledge that objects exist with particular properties seems to be just the kind of knowledge that would be useful for us to have. Now, there still might be reason to think that Locke is using the technical sense of assurance when describing sensitive knowledge. For, Rickless argues, only the Assurance View can make sense of the claim that sensitive knowledge is less certain than intuitive and demonstrative knowledge (Rickless, forthcoming). On the Assurance View, intuitive and demonstrative knowledge are certain whereas sensitive knowledge is merely a highly probable judgment. So the Assurance View can easily explain why sensitive knowledge is less certain than intuitive and demonstrative knowledge. On the Knowledge View, there are three degrees of certainty: intuitive knowledge is the most certain, demonstrative knowledge is less certain than intuitive knowledge but more certain than sensitive knowledge, and sensitive knowledge is the least certain kind of knowledge. Thus the Knowledge View can appeal to the relative uncertainty of demonstrative knowledge (with respect to intuitive knowledge) in order to explain the relative uncertainty of sensitive knowledge (with respect to both intuitive and demonstrative knowledge): just as demonstrative knowledge is less certain than intuitive knowledge and yet is still certain, sensitive knowledge can be less certain than demonstrative and yet still be certain. Rickless objects to this line of argument, Nathan Rockwood 8 though, because Locke does not ever explicitly say that demonstrative knowledge is "less certain" than intuitive knowledge. Locke says instead that demonstrative knowledge is less "clear", less "bright", and "more imperfect" (E IV.ii.1, 530; IV.ii.4, 532; IV.ii.6, 533; IV.ii.7, 534). Rickless argues: What this means is that, for Locke, the degrees of knowledge are degrees of clarity or perfection, but not degrees of certainty: intuitive and demonstrative knowledge are equally certain, but not equally clear or perfect. (Rickless, forthcoming, my emphasis) For Rickless, there is only one degree of certainty. "If this is so," he continues, "then one cannot appeal to whatever distinguishes the certainty of demonstrative knowledge from the certainty of intuitive knowledge to explain the lesser degree of certainty of sensitive knowledge" (Rickless, forthcoming). But contrary to Rickless's claim that "intuitive and demonstrative knowledge are equally certain" (Rickless, forthcoming), demonstrative knowledge is less certain than intuitive knowledge. Locke says that intuitive knowledge is the "most certain" kind of knowledge (E IV.ii.1, 531, my emphasis), and that intuitive knowledge of our own existence "come[s] not short of the highest degree of certainty" (E IV.ix.3, 619, my emphasis). If intuitive knowledge is the "most certain" and the "highest degree of certainty", then that means demonstrative knowledge must be less certain. After intuitive knowledge, Locke says "the next degree of knowledge" is demonstrative knowledge (E IV.ii.1, 531, my emphasis). That demonstrative knowledge is the second degree of knowledge suggests that it is also the second degree of certainty. This is confirmed when Locke introduces sensitive knowledge: "These two, (viz.) intuition and demonstration, are the degrees of our knowledge," and then he goes on to introduce sensitive knowledge saying that it does not reach "either of the forgoing degrees of certainty" (E IV.ii.14, 537). Intuitive and demonstrative knowledge are different "degrees of certainty" (in the plural). Nathan Rockwood 9 So on Locke's view, it is possible to be a lower degree of certainty (relative to another degree of knowledge) and yet still be certain. The case for the Assurance View is based on three arguments which at first seem plausible, but on closer inspection each argument has significant problems. One argument is that sensitive knowledge merely "deserves" and "passes under" the name of knowledge. But Locke may be saying that sensitive knowledge "deserves" and "passes under" the name of knowledge because it is knowledge, which is consistent with his use of those phrases elsewhere. Another argument is that Locke uses the term "assurance" to describe sensitive knowledge, and "assurance" is sometimes used as a technical term to refer to highly probable judgment that falls short of certain knowledge. However, Locke elsewhere uses the term "assurance" to describe certain knowledge, and so Locke's use of that term does not undermine the status of sensitive knowledge as a kind of certain knowledge. Finally, Rickless argues that there is only one degree of certainty, and since sensitive knowledge is less certain that intuitive and demonstrative knowledge it follows that sensitive knowledge is not a kind of certain knowledge. In response, though, I have shown that for Locke there are degrees of certainty. Consequently, sensitive knowledge can be less certain than the other degrees of knowledge just as demonstrative knowledge is less certain than intuitive knowledge. Each of the primary reasons for holding the Assurance View, therefore, are unpersuasive. §4 The Case for the Knowledge View The case for the Knowledge View is simple. Locke calls sensitive knowledge because it is knowledge. There are "three degrees of knowledge, viz. intuitive, demonstrative, and sensitive" (E IV.ii.14, 538). Although sensitive knowledge is the lowest degree of knowledge, it Nathan Rockwood 10 is still a degree of knowledge. That sensitive knowledge is genuine knowledge (and not merely given the honorific appellation "knowledge") is confirmed by the very next sentence where Locke says that "in each" degree of knowledge "there are different degrees and ways of evidence and certainty" (E IV.ii.14, 538). So sensitive knowledge is one degree of knowledge with its own evidence and certainty. In Locke's view "to know and be certain, is the same thing" (Stillingfleet, W4: 145), and yet Locke repeatedly claims that sensitive knowledge is certain. there is a "certainty of our senses" (E IV.xi.2, 630-631, my emphasis); sensitive knowledge "is a certainty" (E IV.xi.2, 631, my emphasis); "nobody can, in earnest, be so skeptical as to be uncertain of the existence of those things which he sees and feels" (E IV.xi.3, 631, my emphasis); we can have "certain knowledge that...[our] seeing hath a cause without" (E IV.xi.5, 632, my emphasis); no one else has "as certain and clear a knowledge of the flood as Noah", for only Noah was there to actually see the flood (E IV.xviii.4, 691, my emphasis); finally, there are "three degrees of knowledge", and "in each" there is "certainty" (E IV.ii.14, 538). While Locke acknowledges that sensitive knowledge is a lower degree of certainty, he also repeatedly insists that sensitive knowledge is certain. Therefore, sensitive knowledge must be genuine knowledge. Sensitive knowledge also satisfies the definition for knowledge. Locke defines knowledge as the perception of a relation between ideas: Knowledge then seems to me to be nothing but the perception of the connexion and agreement, or disagreement and repugnancy of any of our ideas. (E IV.i.2, 525) Any perception of the relevant kind of relation between ideas counts as knowledge. As Locke says, "Where this perception is, there is knowledge, and where it is not...we always come short of knowledge" (E IV.i.2, 525). By contrast, probable judgment is when the relation between ideas "is not perceived, but presumed to be so" (E IV.xiv.4, 653, my emphasis). The debate between Nathan Rockwood 11 the Knowledge View and the Assurance View, then, is whether Locke takes sensitive knowledge to be the perception or the presumption of a relation between ideas. Perhaps the best evidence in the Essay that Locke takes sensitive knowledge to be the perception of a relation between ideas comes just after he restates his definition of knowledge: Knowledge, as has been said, lying in the perception of the agreement, or disagreement, of any of our ideas, it follows from hence, that... we can have no knowledge farther, than we can have perception of that agreement, or disagreement: which perception being, 1. either by intuition... or, 2. by reason [i.e. demonstration]... or, 3. by sensation, perceiving the existence of particular things. (E IV.iii.1-2, 538-539, my emphasis) Locke recapitulates his official definition of knowledge as the perception of a relation between ideas, and then says that this perception is either by intuition, by reason, or by sense perception (the three degrees of knowledge and certainty). This passage indicates, then, that Locke takes sensitive knowledge to be the perception of a relation between ideas. Further, in his correspondence with Stillingfleet, Locke specifies what the two ideas in sensitive knowledge are that are perceived to agree: Now the two ideas, that in this case are perceived to agree, and do thereby produce knowledge, are the idea of actual sensation...and the idea of actual existence of something without me that causes that sensation. (Stillingfleet, W4: 360, my emphasis) Here Locke clearly indicates that sensitive knowledge is the perception of a relation between ideas and that this perception does "thereby produce knowledge". He even says that "the perceived connexion of those two ideas" produces the "utmost" certainty that we could have concerning this matter (Stillingfleet, W4: 360). Rickless is forced to acknowledge that this passage is "flatly irreconcilable" with the Assurance View (Rickless 2008, p. 98). Rickless suggests: Perhaps under pressure from Stillingfleet, who worries explicitly about the fact that Locke's theory appears to leave room for external world skepticism, Locke backtracks, insisting he does not refuse the possibility of knowledge (as opposed to mere judgment) of the existence of sensible extra-mental objects. (Rickless 2008, p. 98). Nathan Rockwood 12 However, there is no need to interpret Locke as flatly contradicting himself, or buckling under pressure from Stillingfleet. Moreover, Locke characterizes sensitive knowledge as the perception of a relation between ideas even in the Essay. This passage in the Stillingfleet correspondence is just further evidence that Locke held this view all along (cf. Newman 2004, pp. 279-280). Locke takes sensitive knowledge to meet the definition for knowledge. When Locke reiterates his definition of knowledge as the perception of a relation between ideas, he affirms that we can perceive this relation between ideas "by sensation" (E IV.iii.1-2, 538-539). He also identifies "the two ideas, that in this case are perceived to agree" as the idea of sensation and the idea of an external object causing that sensation, and he affirms that the perception of the relation between these ideas does "thereby produce knowledge" (Stillingfleet, W4: 360). So Locke sees sensitive knowledge as the perception of a relation between ideas rather than as the presumption of a relation between ideas. Therefore, sensitive knowledge is genuine knowledge rather than mere probable judgment. Rickless argues, though, that the perception of this relation must be either immediate or mediate. If the perception of the relation is immediate (i.e. done in one step), then it is intuitive knowledge (E IV.ii.1, 530-531). If the perception of the relation is mediated by other ideas (i.e. done in multiple steps), then it is demonstrative knowledge (E IV.ii.2-3, 531). These appear to be mutually exclusive options. There is no logical space, then, for sensitive knowledge to be a third kind of knowledge (Rickless 2008, p. 97; Rickless, forthcoming). If sensitive knowledge were genuine knowledge, then it would have to collapse back into either the immediate perception or mediate perception of ideas, and so collapse into either intuitive or demonstrative knowledge. Since sensitive knowledge is meant to be distinct from intuitive and demonstrative knowledge, sensitive knowledge must not be the perception of a relation between ideas. Nathan Rockwood 13 Rickless pushes the proponents of the Knowledge View to state what this third kind of perception of a relation between ideas is supposed to be. But if proponents of the Knowledge View have not yet clearly articulated how sensitive knowledge is supposed to be a third kind of perception of a relation between ideas, it is because Locke did not clearly articulate it either. However, Locke does commit himself to the view that sensitive knowledge is the perception of a relation between ideas. So even if Locke should not think that sensitive knowledge is a third kind of perception of a relation between ideas, he does think this. Furthermore, I think it is possible for there to be (in some sense) a third category of perceiving a relation between ideas. Rickless is right that any perception of a relation between ideas must be immediate or mediate. Suppose that in sensitive knowledge we mediately perceive a relation between the idea of sensation and the idea of an existing object, and so sensitive knowledge counts as a kind of demonstrative knowledge. Locke still might want to distinguish sensitive knowledge from all other instances of demonstrative knowledge. He can make such a distinction by appealing to the content of the demonstration: the mediate perception of a relation between the idea of sensation and the idea of an existing object will count as sensitive knowledge, whereas the mediate perception of a relation between any other two ideas will count as a demonstration. So sensitive knowledge might be a kind of demonstration that is important enough to merit its own category. This suggestion that sensitive knowledge is a specific kind of demonstration comes with a caution, however. For Rickless rightly objects that if sensitive knowledge is a special kind of demonstration then we need a good explanation for why sensitive knowledge is less certain demonstrative knowledge (Rickless, forthcoming). If sensitive knowledge is just another demonstration, then it seems that sensitive knowledge and demonstrative knowledge would be Nathan Rockwood 14 equally certain. Moreover, there are probably longer and more complicated demonstrations than the proof for external objects, and so it would seem that those demonstrations would be less certain than sensitive knowledge (Rickless, forthcoming). Yet Locke insists that sensitive knowledge is less certain than demonstrative knowledge. Rickless doubts that any satisfactory explanation can be given. I am more optimistic. Lex Newman, for example, argues that sensitive knowledge includes both the perception of a relation between ideas and a probabilistic judgment that our ideas correspond to external objects (Newman 2004, pp. 283, 285; Newman 2007, p. 325). Sensitive knowledge counts as knowledge because it includes the perception of a relation between ideas. Yet, on Newman's interpretation, sensitive knowledge also includes a probabilistic judgment that our ideas correspond to external objects, and this judgment might be wrong. The fallibility of this judgment, then, explains why Locke takes sensitive knowledge to be less certain than the other degrees of knowledge. Although I am not here endorsing Newman's view, it does serve as an example of how we could take sensitive knowledge to be a kind of demonstrative knowledge (a perception of an agreement between ideas) and still have an explanation for why sensitive knowledge is less certain than demonstrative knowledge (namely, because it also includes a probabilistic judgment that an external object corresponds to an external object). Further, even if we do not have a satisfactory explanation for why Lock thinks that sensitive knowledge is less certain than demonstrative knowledge, it is clear that Locke thinks that sensitive knowledge is less certain than demonstrative knowledge. It is also clear that Locke takes sensitive knowledge to be the perception of a relation between ideas. These commitments together entail that Locke thinks that sensitive knowledge is (somehow) a third kind of Nathan Rockwood 15 perception of a relation between ideas. Again, perhaps Locke should not think this, but he does think this. I have argued that, according to Locke, sensitive knowledge is certain and that it satisfies the definition of knowledge. And then there is the fact that Locke calls it knowledge. I conclude, then, that according to Locke sensitive knowledge is genuine knowledge.7 Bibliography Keith Allen, "Locke and Sensitive Knowledge," The Journal of the History of Philosophy vol. 51, n. 2 (April 2013). Silvio Seno Chibeni, "Locke on the Epistemological Status of Scientific Laws," Principia: an International Journal of Epistemology vol. 9, n. 1-2 (December 2005). James Gibson, Locke's Theory of Knowledge and its Historical Relations (Cambridge University Press 1960) Locke, John, An Essay Concerning Human Understanding, Edited by Peter H. Nidditch (Clarendon Press 1975). Jennifer Nagel, "Sensitive Knowledge: Locke on Skepticism and Sensation," The Blackwell Companion to Locke, ed. Matthew Stuart (Blackwell, forthcoming). Lex Newman, "Locke on Sensitive Knowledge and the Veil of Perception – Four Misconceptions," Pacific Philosophical Quarterly, vol. 85 (2004). –– "Locke on Knowledge," The Cambridge Companion to Locke's "Essay Concerning Human Understanding", ed. Lex Newman (Cambridge University Press 2007) David Owen, "Locke on Sensitive Knowledge," David Owen's papers: http://www.ic.arizona.edu/ic/dwo/David%27s%20Papers/papersind.htm (dated December 2008; accessed September 2012) Samuel C. Rickless, "Is Locke's Theory of Knowledge Inconsistent?" Philosophy and Phenomenological Research, vol. 77, n. 1 (July 2008) –– "Locke's 'Sensitive Knowledge': Knowledge or Assurance?" Oxford Studies in Early Modern Philosophy, forthcoming Nathan Rockwood 16 7 I would like to thank Lex Newman, Samuel Rickless, and the anonymous referee of this journal for their comments on earlier drafts this paper.