on hume’s deontological response to scepticism

February 4, 2021 · hume/scepticism


In Hume’s Deontological Response to Scepticism (HDRS), Hsueh Qu from the National University of Singapore provides a novel interpretation of Hume’s take on the sceptical system of philosophy.1 At the end of Part IV of A Treatise of Human Nature, Book I (THN 1.4), Hume illustrates the Dangerous Dilemma bound to befall anyone deeply considering a sceptical outlook on their world: if we are to remain sceptical of all things, we must be sceptical of (and may condemn) all reasoning, which is devastative, and if we then avoid scepticism altogether, we are reduced to credulity, of which we should only be ashamed — in his words, we have “no choice left but betwixt a false reason and none at all”.2 In his paper, Qu takes this dilemma as something less a paradoxical quagmire, and instead a false dichotomy between two deontological extremes. Though Hume is often interpreted as a virtue ethicist,3 4 Qu claims that his discussion on scepticism indeed provides the basis for a deontological framework which is bookended by two extremes: the duty to incessantly reflect, and the absolute lack of duty to reflect whatsoever.

The first portion of Qu’s analysis contains a discussion on the supererogatory nature of Hume’s ethics, namely the distinction between actions which are virtuous but naturally human, and those which are unique and laudable. Secondly, he translates the Dangerous Dilemma before spending most of the work outlining his aforementioned deontologist framework latent in Hume’s response to scepticism. Finally, Qu takes the last bit of his paper to talk briefly about the relationship between Hume’s ethics and his epistemology, naming the ability to integrate the two as a particular benefit of his framework. In this essay, I will provide a brief overview of Qu’s paper, by first defining supererogation and summarizing Hume’s response to scepticism as it is in HDRS. Then, I will outline a visual interpretation of Qu’s framework to provide a basis for further discussion on the idea.

hume and supererogatory actions

A foundational aspect of Qu’s deontological framework is the concept of supererogatory actions. He references Urmson (1958) to define supererogatory actions, reiterating Urmson’s claim “there are many kinds of action that involve going beyond duty proper, saintly and heroic actions being conspicuous examples of such kinds of action,” and stating “there is a class of supererogatory actions such that they [are not] required of us as a duty, but are nevertheless good to do”.5 In other words, supererogatory actions are those deserving of praise, even though we are not obligated to perform them. Clearly, to have supererogatory actions, we must have required or dutiful ones, and with this in mind, Qu starts to build his deontological foundation.

Hume claims (and Qu reiterates) that an action is virtuous if it “pleases us after a certain manner,” and that, “when the neglect, or non-performance of it, displeases us after a like manner, we say that we lie under an obligation to perform it” (THN With this, Qu is equipped to walk us to the conclusion that Hume does leave room for obligation or duty in his ethics, and that those duties can be defined quite clearly using THN in tandem with a new deontological framework. Furthermore, once it is established Hume will allow for responsibility in ethics, Qu pinpoints evidence in THN there exist actions more deservable of praise than others. For example,

“[…] goods, which are common to all mankind, and have become familiar to us by custom, give us little satisfaction; tho’ perhaps of a more excellent kind, than those on which, for their singularity, we set a much higher value.” (THN

With this as a starting block, Qu is then equipped to bolster his framework with the delineation of supererogatory actions by identifying particular traits these actions may have (e.g., rarity, as illustrated in the above quote). Qu’s section on the supererogatory is short, but it is sufficiently sized to introduce the notion, which is crucial if we are to incorporate a core aspect of Hume’s ethics (and epistemology) into a well-defined deontological framework: agreeableness in reasoning cause and effect.

cause and effect

One of the most poignant observations made by Hume considers the nature of cause and effect.

“When an object appears, that resembles any cause in very considerable circumstances, the imagination naturally carries us to a lively conception of the usual effect, tho’ the object be different in the most material and most efficacious circumstances from that cause.” (THN

Put another way, when we perceive an event, our natural inclination is to interpret the event as the result of that which most closely resembles a cause, no matter the possibility they are entirely unrelated. For instance, as I sit writing this essay, I take a drink from my glass, and presently place the glass on the table. The sound I hear is immediately inferred as the result of my placing the glass on the table. In my experience, placing a glass on a table will almost always produce a similar sound, but with my headphones in (as they are now), this sound could just as easily be the result of someone knocking on my door in a very particular way, or some textural element of the ambient music I’m listening to. This conflation of object and cause (or effect) is the first of Hume’s General Rules of Prejudice, specifically described as an “unphilosophical” way of drawing inference. Qu coins this the first influence of the general rules, underpinning the first horn of the deontological interpretation of the Dangerous Dilemma — credulity.

The second general rule is a bit more subtle,

“[…] when we take a review of this act of the mind, and compare it with the more general and authentic operations of the understanding, we find it to be of an irregular nature, and destructive of all the most establish’d principles of reasonings; which is the cause of our rejecting it.” (THN

Essentially, this is where Hume calls for “a review of” or (as Qu puts it) a “reflection on” our inference, considering our human fallibility of reasoning, and dispelling any conclusions drawn from the former general rule.6 As Hume states, this second rule “implies the condemnation of the former” (THN Qu makes it clear that the second influence is taking a review of our mental states, faculties, and intellectual understanding, not reviewing the objects or causes themselves in some abstract way. He coins this the second influence of the general rules, underpinning the second horn of the interpretation — incessant reflection.

Importantly, Qu claims there is a requirement for this kind of reflection under Hume’s ethics and epistemology, that we are called to “continually make higher-order judgements on the reliability of our judgements” (p. 747). As preferable as this reflection and second influence sounds, Hume cautions us that it too leads to a bitter end. Qu points out in THN, we find evidence of Hume’s disquietude when he explains that reflection “on the natural fallibility of [our] judgment” leads to scrutiny against every successive conclusion we draw, and eventually, “all the rules of logic require a continual diminution, and at last a total extinction of belief and evidence” — epistemic apocalypse.7

So, this is the Dangerous Dilemma, one between two horns: total credulity and epistemic apocalypse.8 In this most dismal of places, Qu finds light at the end of the tunnel with three discoveries: Hume’s stance on “safe and agreeable” notions, his preference for science and philosophy, and his chagrin for superstition. For the first, Qu cites many examples in THN where Hume makes clear we “ought to prefer that which is safest and most agreeable” (THN For the latter two, regardless of the distinct definition of “safe and agreeable”, Qu cites Hume’s endorsement of our common-life beliefs (e.g., science and philosophy) precisely because they are more agreeable (p. 761), and his rejection of superstitions precisely because they are not (p. 753). Here now, Qu calls for a mechanism by which we can steer clear of the first horn through the reflection of our faculties, enough to avoid the acceptance of superstition, but not so much so that we destroy science and philosophy: a deontological threshold.

after the threshold

To recap, the sceptical thinker is bound to the shackles of a Dangerous Dilemma, a choice “betwixt a false reason and none at all” (THN Neither horn of this dilemma is acceptable, but there are realms between the bookends which are preferable, like science and philosophy, and those which should be denounced, like superstition. We know that we ought to prefer that which is safe and agreeable, and that reflection is a necessity. Further, there is evidence that Hume allows for requirement and responsibility in his ethics, with room for supererogation.

Putting all these components together, Qu’s designs his deontological framework. I visualize this framework as two concentric circles circumnavigating a singular central point. In the space outside these circles is the World of Credulity, where we abide only by the first influence. Once we embrace reflection on our faculties, we cross the deontological threshold into the domain between the two circles, the acceptable Domain of Reflection. When reasoning leads to conclusions which are safest and agreeable, attraversiamo, we cross into the inner circle, the Place of Supererogatory Reflection. The point at the very center of these two circles represents the Singularity of Epistemic Apocalypse. Strangely, this is a target whose Bull’s Eye we must avoid. Nevertheless, we are obligated to aim for the target, never to stray outside of the outermost circle. Using this analogy, I’ll attempt to describe Qu’s model.

The World of Credulity is described by Qu as “unambiguously culpable, even at the level of common-life” (p. 757). Roughly, Qu characterizes this world as one where individuals are not abiding by their duty to reflect, where they are susceptible to superstition which is not at all agreeable or safe.9 Past the deontological threshold which we are obligated to cross, lies the Domain of Reflection. Here, individuals treat their mental faculties and reasonings with at least a modicum of scepticism, reflecting in such a way that they fulfill their epistemological duty as dictated by Qu-Hume. In the Domain of Reflection, we find such examples as The English Gentleman described in THN After only briefly commenting on the visibly condescending nature of this moniker, Qu describes these individuals as ones who reflect only to the point at which they are required. As Hume puts it, they “do not seek to make themselves philosophers”, but they limit their reflection to form generally reliable beliefs (p. 757).10 If we live our lives in the Domain of Reflection, in the words of Qu, “we do what we are required to do, but nothing more.” Though, simply because we are not obligated to do more reflection past this point does not mean that more is not good.

Recall from a previous section that supererogatory reflection is not required of us as a duty, but is nevertheless good to do. Qu insists the kind of reflection that falls under this category includes science and philosophy. Uniquely, if done successfully, this sort of reflection yields conclusions which are not only safe and agreeable, but unique and laudatory (THN In other words, it is precisely the agreeableness and rarity that gives this kind of supererogatory reflection its significance. Finally, and Qu says it best:

“Since the extreme level of reflection that leads to excessive scepticism is not required as a duty, nor is it good beyond the bounds of duty, we have every reason to reject it.” (p. 763)

With this, Qu provides instruction on how we avoid the Bull’s Eye: we simply do, as that level of reflection is strictly not required of us.


Dealing within the Dangerous Dilemma is a dangerous game. In his paper, Qu provides a strategy: reinterpret the sceptical discussion in Hume’s A Treatise of Human Nature from a deontological perspective.

Qu illustrates first that Hume allows for responsibility and duty, referencing Hume’s encouragement of actions which are virtuous and his disparaging those which are not. Next, Qu shows how we can view the dilemma as a false dichotomy between the duty to incessantly reflect (the second influence of general rules), and the absolute lack of duty to reflect whatsoever (the first influence). Finally, he is able to shape the way we may view intellectual reflection as an epistemic obligation, carefully describing where it is required and where it is supererogatory. The key piece of this design is the deontological threshold. With this mechanism, we allow not only for duty in reflection (deontology in Hume’s epistemology and ethics), but for agreeableness in responsibility (Hume’s epistemology and ethics in deontology). With these components tutti, we define Hume’s Deontological Response to Scepticism.


Hume, David (1975). A Treatise of Human Nature (2nd ed.). L. A. Selby-Bigge and P. H. Nidditch (Eds.). Clarendon Press.

Qu, Hsueh (2019). Hume’s Deontological Response to Scepticism. Ergo, 6(27), 743-769. https://doi.org/10.3998/ergo.12405314.0006.027

Swanton, Christine (2007). Can Hume Be Read as a Virtue Ethicist? Hume Studies, 33(1), 91–113. https://doi.org/10.1353/hms.2011.0234

Taylor, Jacqueline (2006). Virtue and the Evaluation of Character. In Saul Traiger, S. (Ed.), The Blackwell Guide to Hume’s Treatise (276–295). Blackwell. https://doi.org/10.1002/9780470776377.ch15

Urmson, J. O. (1958). Saints and Heroes. In A. Melden (Ed.), Essays in Moral Philosophy (198–216). University of Washington Press.

  1. Qu, Hsueh (2019). Hume’s Deontological Response to Scepticism. Ergo, 6(27), 743-769. https://doi.org/10.3998/ergo.12405314.0006.027 ↩︎

  2. Hume, David (1975). A Treatise of Human Nature (2nd ed.). L. A. Selby-Bigge and P. H. Nidditch (Eds.). Clarendon Press. ↩︎

  3. Taylor, Jacqueline (2006). Virtue and the Evaluation of Character. In Saul Traiger, S. (Ed.), The Blackwell Guide to Hume’s Treatise (276–295). Blackwell. https://doi.org/10.1002/9780470776377.ch15 ↩︎

  4. Swanton, Christine (2007). Can Hume Be Read as a Virtue Ethicist? Hume Studies, 33(1), 91–113. https://doi.org/10.1353/hms.2011.0234 ↩︎

  5. Qu 2019 (p. 744). While this definition suffices for the purposes of his paper, Qu only alludes to an element of this concept which I think could be better addressed: the question of its discreteness. Qu recognizes a particular difficulty faced by supererogation in the eye of deontological ethics, that is how we measure actions beyond the deontological threshold of duty. In other words, if an action meets the deontological threshold and is then to be measured by something other than duty, we reach a point where duty plays second fiddle to some other gauge of “goodness” which is seemingly in conflict with the “responsibility” inherent in deontological ethics. In HDRS (p. 744), Qu lists a few deontologists who deny the consistency of supererogation for this reason. Of course, Qu allows for supererogation as it is a centerpiece of his Humian deontological framework. But, the issue with discreteness goes beyond this fact, in that we must ask, “if we aim to measure actions beyond the deontological threshold, why not acknowledge the existence of super-supererogatory actions beyond the supererogatory threshold, and so on?” This recursive sequence, I think, may be another weakness of supererogation in a deontological system. On the other hand, if we grant supererogation as a continuous measure, it seems to jive a bit more closely with the subsequent claims we will see Qu make regarding more-than-dutiful actions in Hume’s ethics; these I will describe in a later section. ↩︎

  6. See THN for Hume’s use of “review of”, and HDRS, p. 747 for an example of Qu’s use of “reflection”. ↩︎

  7. It’s worth noting Qu reads this last quote as an insinuation that in this situation the extinction of belief and evidence is required by all the rules of logic (p. 751). But, the full quote from that section of THN implies to me the scrutiny of our reasoning leads to a diminution of the rules of logic (for one consequence), and this point marks the turning point for all belief and evidence to be rendered extinct (secondarily). Either way, an epistemic apocalypse is implied. ↩︎

  8. At this point, even Hume states “For my part, I know not what ought to be done in the present case” (THN., a powerful indication of the pickle this dilemma puts us in. ↩︎

  9. Hume is famously quoted in THN “Generally speaking, the errors in religion are dangerous; those in philosophy only ridiculous.” ↩︎

  10. I for one would argue that these days, most people lie in the Domain of Reflection. I’d also posit that, alas, the World of Credulity is not an empty one. ↩︎