© LOGOS & EPISTEME, VI, 1 (2015): 141-146 DIFFERENCE-MAKING AND EASY KNOWLEDGE: REPLY TO COMESAÑA AND SARTORIO Erik J. WIELENBERG ABSTRACT: Juan Comesaña and Carolina Sartorio have recently proposed a diagnosis of what goes wrong in apparently illegitimate cases of 'bootstrapping' one's way to excessively easy knowledge. They argue that in such cases the bootstrapper bases at least one of her beliefs on evidence that does not evidentially support the proposition believed. I explicate the principle that underlies Comesaña and Sartorio's diagnosis of such cases and show that their account of what goes wrong in such cases is mistaken. KEYWORDS: easy knowledge, bootstrapping, Juan Comesaña, Carolina Sartorio Comesaña and Sartorio have recently proposed a novel and elegant diagnosis of what goes wrong in apparently illegitimate cases of 'bootstrapping' one's way to excessively easy knowledge.1 Here I explain their diagnosis of such cases and show that it is mistaken. Their analysis of easy knowledge cases rests on the following principle: E evidentially supports P (given a background of evidence B) only if the absence of E does not evidentially support P (given the same background B).2 They advance this principle in an attempt to formulate a plausible and precise version of the intuitive but somewhat vague thought that a given body of evidence justifies a given belief only if the evidence makes the right sort of difference with respect to the belief. Their proposal is that the evidence makes the right sort of difference to the belief only if the absence of the evidence does not also support the belief. Their explication and defense of the principle make it clear that 'the absence of E' in the principle means the negation of E.3 Thus, the principle can be stated more precisely this way: 1 Juan Comesaña and Carolina Sartorio, "Difference-Making in Epistemology," NOUS 48, 2 (2014): 368-87. 2 Comesaña and Sartorio, "Difference-Making," 374. 3 Comesaña and Sartorio, "Difference-Making," 376. Erik J. Wielenberg 142 Epistemic DM2: E evidentially supports P (relative to a background of evidence B) only if it's not the case that not-E evidentially supports P (relative to B).4 As Comesaña and Sartorio note, Epistemic DM2 "gives a non-reductive condition on evidential support."5 The right-hand side of the principle employs the concept of evidential support and hence the principle "cannot be used in the traditional project of defining propositional knowledge in wholly non-epistemic terms."6 Accordingly, Comesaña and Sartorio seek to motivate the philosophical usefulness of Epistemic DM2 by making the case that it can shed light on cases of easy knowledge. They provide the following example of such a case: Imagine a subject, Roxanne, who looks at an object in front of her "with her wellfunctioning eyes open, in a well-lit environment, in the absence of factors that would make the object look a different color than it is" and employs the following reasoning:7 Reasoning A (1) The object in front of me looks red. So, (2) the object in front of me is red. Therefore, (3) my color vision didn't deceive me this time. Some epistemological theories appear to imply that Roxanne can come to know (3) just on the basis of (1) and furthermore that by engaging in similar reasoning on a variety of occasions while looking at various-colored objects, Roxanne can build a solid inductive case for the reliability of her color vision, thereby arriving at knowledge that her color vision is reliable. Many philosophers find such a procedure to be illegitimate and hold that any epistemological theory that licenses such a procedure is flawed.8 4 Or: relative to a given background of evidence, it's not the case that: (E evidentially supports p and not-E evidentially supports p). "Epistemic DM2" is Comesaña and Sartorio's label for the principle. 5 Comesaña and Sartorio, "Difference-Making," 378. 6 Comesaña and Sartorio, "Difference-Making," 378. 7 Comesaña and Sartorio, "Difference-Making," 380. 8 Reliabilism is a popular target of this sort of objection; see, e.g., Jonathan Vogel, "Reliabilism Leveled," The Journal of Philosophy 97, 11 (2000): 602-23. Stewart Cohen argues that any epistemological theory that has what he calls a "basic knowledge structure" is susceptible to the problem of easy knowledge. A distinctive feature of such theories is that they reject the principle that a potential knowledge source K can yield knowledge for S only if S knows K is reliable; see Stewart Cohen, "Basic Knowledge and the Problem of Easy Knowledge," Philosophy and Phenomenological Research 65, 2 (2002): 309-29. Difference-Making And Easy Knowledge: Reply To Comesaña And Sartorio 143 Comesaña and Sartorio's aim is not to defend any particular epistemological theory against the problem of easy knowledge but rather to "explain what exactly is wrong with cases of easy knowledge, or with a theory that allows that we can come to know 3 just on the basis of 1."9 They argue that Epistemic DM2 implies that (1) does not evidentially support (3) and that is why Roxanne cannot know (3) on the basis of (1).10 To establish the claim that Epistemic DM2 implies that (1) does not evidentially support (3), Comesaña and Sartorio argue that if (1) evidentially supports (3), then not-(1) also evidentially supports (3) – which is incompatible with Epistemic DM2. To make the case that if (1) evidentially supports (3) then not-(1) does as well, they suggest that the following line of reasoning is just as plausible as Reasoning A: Reasoning B Not-(1): it's not the case that the object in front of me looks red. So, not-(2): it's not the case that the object in front of me is red. Therefore, (3) my color vision didn't deceive me this time. If, as they claim, Reasoning B has approximately the same plausibility as Reasoning A, then the assumption that Reasoning A is plausible and hence (1) evidentially supports (3) yields the result that Reasoning B is plausible and hence not-(1) also evidentially supports (3). Since Epistemic DM2 excludes the possibility that both (1) and not-(1) evidentially support (3), Epistemic DM2 implies that (1) does not evidentially support (3). On Comesaña and Sartorio's view, then, what is illegitimate about the sort of bootstrapping that occurs in cases of easy knowledge is that the bootstrapper bases at least one of her beliefs on evidence that does not evidentially support the proposition believed, and the defect in any epistemological theory that licenses such bootstrapping is that the theory runs afoul of Epistemic DM2. I think that this diagnosis of what goes wrong in cases of illegitimate bootstrapping is mistaken. While the particular case that Comesaña and Sartorio discuss does involve a violation of Epistemic DM2, there are other cases of apparently illegitimate bootstrapping that do not. It turns out that the fact that the color vision case violates Epistemic DM2 is a consequence of specific features of that case that are absent in other paradigmatic cases of easy knowledge. To see this, consider a version of Vogel's Roxanne case.11 Suppose that Roxanne has no 9 Comesaña and Sartorio, "Difference-Making," 380. 10 Comesaña and Sartorio, "Difference-Making, "373-4. 11 Vogel, "Reliabilism Leveled," 602-23. Erik J. Wielenberg 144 idea whether her car's fuel gauge is reliable. She checks the fuel gauge and reasons as follows (where 'X' indicates some precise level of fuel in the tank – e.g completely full, 5/8 full, 1/3 full): Reasoning C (4) The gas gauge indicates X. So, (5) the gas tank is X. Therefore, (6) on this occasion, the reading on the gauge corresponded exactly to the amount of gas in the tank. As before, Roxanne can use the same sort of reasoning on multiple occasions to build a solid inductive case for the reliability of the gas gauge. So, suppose she draws on multiple instances of reasoning C to arrive at: (7) The gas gauge is very reliable – it's disposed to indicate the level of fuel in the tank with a high degree of accuracy. Suppose that (4) evidentially supports (7) in the way just sketched. If Comesaña and Sartorio's diagnosis of what goes wrong in cases of easy knowledge is correct, then it must be the case that if (4) evidentially supports (7) then not-(4) also evidentially supports (7). In the case of Roxanne and her color vision, Comesaña and Sartorio employed the strategy of generating a line of reasoning parallel to Roxanne's reasoning that began with the negation of Roxanne's first premise. Applying the same strategy to the present case of Roxanne and the gas gauge yields the following line of reasoning: Reasoning D Not-(4): it's not the case that the gas gauge indicates X. So, not-(5): it's not the case that the gas tank is X. Therefore, (6) on this occasion, the reading on the gauge corresponded exactly to the amount of gas in the tank. The conjunction of not-(4) and not-(5) does not imply (6). Suppose that Roxanne is working with data like the following: on Monday, the gauge didn't indicate 5/8 full and the tank wasn't 5/8 full. On Tuesday, the gauge didn't indicate 1/2 full and the tank wasn't 1/2 full. On Wednesday, the tank didn't indicate 1/3 full and the tank wasn't 1/3 full. These are cases in which the gauge got things right within a very wide margin of error; no number of cases of that sort support the conclusion that the gauge has a high degree of accuracy across a range of situations. Therefore, the strategy that Comesaña and Sartorio employed in the color vision case does not work in the gas gauge case and the claim that if Difference-Making And Easy Knowledge: Reply To Comesaña And Sartorio 145 (4) evidentially supports (7) then not-(4) also evidentially supports (7) is unsupported. Consequently, it appears that Epistemic DM2 fails to capture what is wrong with Roxanne's bootstrapping in the gas gauge case. Furthermore, reflection on this case reveals that the case of Roxanne and her color vision can be modified so that it also does not involve a violation of Epistemic DM2.12 Consider the following modified versions of Reasoning A and Reasoning B from that case, where 'X' indicates some color: Reasoning A' The object in front of me looks X. So, (2) the object in front of me is X. Therefore, (3') my color experience of the object exactly matched the actual color of the object in this case. Reasoning B' Not-(1): it's not the case that the object in front of me looks X. So, not-(2): it's not the case that the object in front of me is X. Therefore, (3') my color experience of the object exactly matched the actual color of the object in this case. While the conjunction of (1) and (2) implies (3'), the conjunction of not-(1) and not-(2) does not imply (3'). Consequently, the assumption that (1) epistemically supports (3') does not imply that not-(1) also epistemically supports (3') and so Epistemic DM2 fails to capture what is wrong with Reasoning A'. Therefore, Epistemic DM2 fails to pinpoint just what is illegitimate about paradigmatic cases of easy knowledge.13 Of course, none of this shows that 12 Thanks to Justin Snedegar for pointing this out. 13 An anonymous referee suggests that there is a principle similar to Epistemic DM2 that handles the two cases of easy knowledge that I have argued Epistemic DM2 cannot handle. The modified principle is: E evidentially supports P only if it's not the case that every alternative to E supports P. While it may not always be obvious what the alternatives to a given proposition are, in the gas gauge case and the modified color vision case the alternatives are intuitively apparent. In the modified color vision case, if E = the object in front of me looks red, then the alternatives to E are: the object in front of me looks blue, the object in front of me looks green, and so on. However, this modified principle succumbs to counterexamples. For example, in the color vision case let E = the object in front of me looks red and let P = I'm currently having a visual experience. Intuitively, E evidentially supports P, yet the modified principle implies that E does not evidentially support P since each of E's alternatives also supports P – i.e. that the object in front of me looks blue evidentially supports the proposition that I am currently having a visual experience, that the object in front of me looks green evidentially supports the Erik J. Wielenberg 146 Epistemic DM2 is false. For all I have said here, Epistemic DM2 may capture an important necessary condition on epistemic support. However, as I noted above, Comesaña and Sartorio offer Epistemic DM2's usefulness in diagnosing what goes wrong in easy knowledge cases as its main philosophical pay-off. But if I am right, then if we want an adequate explanation of what is wrong with cases of easy knowledge, we should look elsewhere.14 proposition that I am currently having a visual experience, and so on. (Note that Epistemic DM2 is not susceptible to this counterexample because not-E (the proposition that it's not the case that the object in front of me looks red) does not evidentially support the proposition that I'm currently having a visual experience). 14 For helpful discussion of the ideas discussed in this paper, I thank Juan Comesaña and Carolina Sartorio. I presented these ideas at a meeting of the Evidence, Justification and Knowledge reading group associated with the Arche Centre at the University of St. Andrews; I thank the other members of that group for their feedback. Jessica Brown and Justin Snedegar read an earlier draft of this paper and made helpful suggestions, for which I am also grateful.