Debasing Scepticism Revisited

by Changsheng Lai

University of Edinburgh


In this essay, I will criticise Brueckner’s objection to debasing scepticism, and then provide a new solution to the debasing demon problem. I will firstly introduce debasing scepticism and highlight its alleged “merit”, i.e., it threatens universal doubt. Some objections to debasing scepticism will be briefly analysed. After that, it will be illustrated that Brueckner’s objection concerning the KK principle is not satisfactory because debasing scepticism can avoid utilizing KK principle. Finally, I will propound a new objection to debasing scepticism by rejecting an essential premise in Schaffer’s argument, namely, evidential position closure. It will be revealed that the closure-like premise is not actually closed and cannot survive an intensive analysis.

  1. Debasing Scepticism

Debasing scepticism challenges our everyday knowledge claims by casting doubt on whether our beliefs are properly based on the relevant evidence – viz., it targets the basing condition: “knowledge requires the production of belief, properly based on the evidence” (Schaffer 2010:232). Traditional deceiving scepticism is motivated by the possibility that a deceiving sceptical scenario might obtain. For example, there seems to be no way to rule out the possibility that we are constantly deceived by an evil demon, or that we are a brain-in-a-vat (See Descartes’ Meditations; Putnam (1982), etc.). Similarly, debasing scepticism typically relies on a “debasing demon” summoned by Schaffer (2010). The demon can undetectably make us believe that our daily beliefs are produced on proper bases (rational reasoning, sufficient evidences, etc.) – even though in fact they are all based on improper bases (e.g., wishful thinking, guessing, superstition). The debasing demon can thus deprive us of everyday knowledge, because it is widely accepted that true beliefs formed on improper bases cannot be counted as knowledge.

It is alleged to be a “merit” of debasing scepticism that it threatens universal doubt by imperilling our knowledge of any proposition, even including the cogito (Schaffer 2010:233). As Brueckner (2011) points out, Schaffer’s debasing demon extends the range of scepticism – traditional (deceiving) scepticism only casts a posteriori knowledge into doubt, because the hypothesis that those a priori truths are false (e.g., 2+2=4) seems metaphysically impossible, as there seems to be no possible world where 2+2 fails to equal 4. Nonetheless, debasing scepticism is alleged to be able to threaten both a posteriori and a priori knowledge – because according to Schaffer, it is always possible to suppose that every proposition that we claim to know, no matter known a priori or a posteriori, is debased.

  1. Debasing Scepticism and KK Principle

Brueckner (2011) famously argues against debasing scepticism by accusing it of resorting to a controversial premise, i.e., the KK principle. He reconstructs Schaffer’s sceptical argument as follows:

  • “(1) If I know T, then my belief of T is properly based. (Premise)
  • (2) If I know T, then I can know that I know T. (Premise)
  • (3) If I can know that I know T, then I can know that my belief of T is properly based. (By (1) and a variant of the Closure Principle)
  • (4) If I know T, then I can know that my belief of T is properly based. (By (2), (3))
  • (5) I cannot know that my belief of T is properly based. (Premise)
  • (6) I do not know T. (By (4),(5))”  (Brueckner 2011:296-297)

Brueckner rejects the second premise as it equals KK principle and KK principle is false (For a more sophisticated formulation of KK principle, see McHugh(2010:231)). Although there are some supportive voices of KK (e.g., see McHugh 2010; Greco 2014), the KK principle is widely regarded as unacceptable because its requirement for knowledge is too demanding. Typically, the principle was intensively attacked by some externalists, e.g., Dretske rejects KK because “factual knowledge, according to modest contextualism, depends for its existence on circumstances of which the knower may be entirely ignorant” (2004:176). Similarly, reliabilists have argued that one may be unaware of the reliable source from which she gains her knowledge of p, thereby be ignorant of the fact that she knows that p. Moreover, the KK principle is suspected of generating an infinite regress (to know that p, one has to know that he knows that p, and know that he knows that he knows that p; and so forth) and thus makes knowledge impossible. Brueckner argues that, given that KK principle is false, debasing scepticism can be rejected.

However, even if we grant that KK principle is unacceptable, Brueckner’s objection is problematic. Firstly, as Ballantyne & Evans point out, Brueckner “takes it for granted that debasing scepticism must go through a particular argument schema” (2013:552). Therefore his objection can be disarmed easily if the sceptic’s argument schema turns out to be different from the one reconstructed by Brueckner. For example, one can reconstruct the sceptical argument based on the underdetermination principle (see Pritchard 2016, Ashton 2015, Boult 2013, etc.), so the second premise can be reformulated as: “If I know that p, then I should have better reason to believe that my belief of p is properly based than that it is not”. In this way, the sceptical conclusion can be derived as well, in the sense that (according to Schaffer’s presumptions) I do not have better reason to believe that my belief of p is properly based rather than debased by the demon. KK principle is thus avoided in this revised argument schema.

Moreover, Schaffer’s original articulated schema of argument seems immune to Brueckner’s criticism. He clarifies his argument structure as follows:

  • “(S1) If one knows that p, then one believes that p on a proper basis;
  • (S2) If one knows that p, then one is in an evidential position to know that one knows that p;
  • (S3) If one is in an evidential position to know that p, and p entails q, then one is in an evidential position to know that q;
  • (S4) So if one knows that p, then one is in an evidential position to know that one believes that p on a proper basis;
  • (S5) One is not in an evidential position to know that one believes that p on a proper basis;
  • (S6) One does not know that p” (2010:234)

 Schaffer prudently avoids using “know” directly in (S2)-(S5), but replaces it with a tricky and ambiguous term “be in an evidential position to know” (hereafter, “epK”) instead, which makes his second premise weaker and thus more plausible than Brueckner’s. Although Schaffer does not articulate what “epK” exactly means, it should be clear that “epK” differs from “knows” in the sense that one can, for example, have a good evidence to believe that p while failing to do so because of misleading defeaters. In that case, the subject can “epK” that p without actually knowing that p. A debased victim controlled by the debasing demon can be another typical example who “epK” that p without knowing that p. With the distinction between “epK” and “knows” in play, whether KK principle applies to Schaffer’s original argument is doubtful. Therefore, I suggest a new objection to debasing scepticism.

  1. The New Objection

Now let us return to Schaffer’s original argument schema. Unlike Bruckner who targets the second premise, I aim to examine the third premise:

  • (S3) If one is in an evidential position to know that p, and p entails q, then one is in an evidential position to know that q.

This can be formalized as:

  • [Evidential Position Closure] epKp ^ (p→q) →epKq

I name this premise EPC as it is closure-like (cf. the standard “known entailment closure”; see Bernecker 2012:368): Kp ^ K(p→q)→Kq). EPC is essential for Schaffer’s argument as it bridges the gap between the possibility of the debasing hypothesis and the violation of the basing condition. Ex hypothesi, the possibility of debasing scenario means that one cannot distinguish a debasing scenario from a non-debasing scenario. One thereby fails to epK daily propositions (because no available evidence can support one’s belief that she is in a debasing scenario better than the opposite scenario). Hence the basing condition of knowledge is violated according to EPC. Without EPC, the mere possibility of the debasing demon cannot suffice for scepticism, because one can argue that knowledge is fallible and does not require ruling out all incompatible alternatives.

However, EPC is false as the closure-like principle is not actually closed, so one’s epistemic status, namely “epK”, cannot be transmitted from the antecedent to the consequent in the way that EPC predicts. Here is a counterexample:

I am in an evidential position to know that I won the lottery by watching my ticket drawn on TV live. However, unbeknownst to me, if I win the lottery, then a man called Jack who I have never heard before, would lose£100 because he bet with his friend Mary that he would win the lottery.

In this case, it is obviously implausible to claim that I “epK” that Jack will lose£100, because I am not in an evidential position to know about Jack’s bet or its consequence – I do not even know who Jack or Mary is. In this counterexample, “p” refers to “I win the lottery”, and “q” refers to “Jack will lose£100 to Mary”, I epK that p, and p entails q. Nonetheless, I do not epK that q, because I do not epK that “pq”. EPC thus fails. A moral that we can learn from this counterexample is: EPC is not closed unless the subject has good evidences to believe that “p→q” (cf. standard closure principle: Kp ^ K(p→q)→Kq).

Naturally, in order to avoid the aforementioned counterexample, one may try to revise EPC as follows:

  • [EPC*] epKp ^ epK(pq)→epKq

I.e. If one is in an epistemic position to know that p, and one is in an epistemic position to know that p entails q, then one is in an epistemic position to know that q. Admittedly, EPC* is seemingly closed. However, this revision might invite inconsistency. If EPC is replaced by EPC*, then the first premise should be correspondingly revised as “I am in an evidential position to know that if one knows that p, then one believes that p on a proper basis”, i.e., “epK(S1)”, so that it can be substituted into EPC* and then derive the sceptical conclusion. However, debasing scepticism promises to threaten universal doubt, so any proposition can be imperilled, including (S1). That is to say, according to (S5): “One is not in an evidential position to know that one believes that p on a proper basis”, one cannot epK that (S1) likewise any other proposition p. After all, there is no evidence can sufficiently support that one’s belief of (S1), likewise one’s belief of “I have both hands”, is not debased. Therefore, the revised first premise is incompatible with (S5). Hence the debasing sceptical argument would be inconsistent if its second premise is replaced by EPC*.

One may attempt to save debasing scepticism by constraining the extension of “p→q” to a priori deductions, e.g., “if I am alive then I am not dead”. In the lottery counterexample, EPC fails because “if I win the lottery then Jack will lose£100” is a posteriori deduction which requires my posteriori knowledge about Jack and his bet. So the lottery counterexample seems cannot disprove EPC.

However, even if “p→q” is a priori, it does not mean that one can epK that “p→q” a priori, so EPC can still fail to be closed. For example, “(√x=3)→(x=9)” is a priori, a three-year-old child who epK that “√x=3” may fail to epK that “x=9”, because he lacks relevant mathematical knowledge, so he does not epK that “(√x=3)→(x=9)”. So debasing scepticism encounters a dilemma here: on one horn, EPC is not closed if the subject does not epK that “p→q”; on another horn, if sceptics endorse that the subject does epK that “p→q”, then the problem of inconsistency aforementioned would occur.

  1. Conclusion

I have demonstrated that Brueckner’s objection to debasing scepticism can be disarmed by adopting different interpretations of Schaffer’s argument schema. Schaffer’s own argument schema is able to evade KK principle and Brueckner’s criticism because Schaffer uses “epK” rather than “knows”. A new objection is thus given, which refutes Schaffer’s own third premise, i.e., evidential position closure, by providing counterexample showing that the transmission of “epK” is not actually closed in EPC. It has been argued that debasing sceptics can neither abandon EPC nor consistently revise EPC. Debasing scepticism is thus rejected.

The author gratefully acknowledges sponsorship from China Scholarship Council for his current research.


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