Reading Group: David Macarthur, 'Naturalism and Skepticism'

Kant called it a veritable scandal for philosophy that claims about the existence of the external world have to be taken on faith. Macarthur echoes this sentiment. He is alarmed by the fact that most philosophers today seem indifferent to this scandal although there is still no satisfactory proof for the existence of the external world. In his view, the culprit is (scientific) naturalism. Naturalism dismisses the epistemological preoccupation with refuting the skeptic as an exaggeration of the underlying problem. It takes external world skepticism (knowledge of the external world is not rationally justified) to be defective in certain respects so that its refutation is no precondition for satisfactory accounts of knowledge. Macarthur concedes that quietism with regard to the skeptical problem is an option. However, he thinks that naturalism lacks the resources for sustaining this option. If that is true, then naturalism simply begs the question against the skeptic and thus exacerbates external world skepticism.

Hume was unambiguous about the skeptical consequences of his naturalism. According to him, all mental processes are causal processes. If all mental processes are causal processes, then subjective experiences are intramental effects of some cause. Intramental effects can be produced by an infinitely large number of causes and for that reason do not allow us to tell what their actual effective causes were. So it may be the case that, contrary to our presumptions, none of these causes issues from the external world. This causal theory of experience results in a systematic mismatch between mind and world which leads to external world skepticism.

Naturalism shares Hume’s premiss but seeks to avoid the conclusion. All attempts to do this, Macarthur argues, are dogmatic in one way or other. (Before he turns to representative naturalistic responses to external world skepticism, he rejects inference to the best explanation as a suitable anti-skeptical instrument. Even if references to the external world explain best what makes our experiences coherent, these reference are pointless if our subjective experiences are not coherent, as seems to be the case on the causal theory of experience. This is simply to reinforce the point that if inference to the best explanation is one of the most powerful tools of naturalism, it cannot hope to refute the skeptic but must settle for the quietist option.)

Macarthur discusses three representative examples for naturalistic responses to external world skepticism. These are

(1) Quine’s position that skepticism cannot doubt all of knowledge at the same time. As far as skepticism merits an answer, there is common ground with science – those bits of empirical knowledge which are not currently in doubt. External world skepticism doubts all of knowledge and thus is unanswerable.

(2) The reliabilist view that replaces rational justification with a causal account of belief formation. If beliefs are produced by reliable processes, we can have true beliefs about the external world without having a subjective experience of its justification. So the skeptic’s view that there is no external world because we do not have rationally justified knowledge of it is badly motivated.

(3) Finally, Strawson’s interpretation of Hume according to which the belief in the external world is natural, not rational. Although what the skeptic says against the external world is intelligible, the lack of rational justifications for beliefs in the external world does not affect the natural commitment to this notion.

Macarthur finds all these responses unsatisfactory. Here are (what I take to be) his main reasons for this assessment:

(ad 1) It is wrong to assume that external world skepticism doubts all of knowledge. It just doubts knowledge about the external world. So external world skepticism is answerable by naturalist standards.

(ad 2) Reliabilism may have a point on possible knowledge. But actual knowledge involves some subjective experience of justification. So the skeptical point retains its force. Furthermore, reliabilism cannot properly account for the reliability of belief-forming processes. Reliability is either posited dogmatically as the property of some process, or accounting for it leads to infinite regress because reliability is accounted for in terms of other reliable processes.

(ad 3) Natural belief cannot be revised or confirmed empirically. This contradicts naturalistic principles. Then, the notion of natural belief obscures the connection between belief and reason. Contrary to assumptions or hypotheses, Macarthur claims, beliefs are always open to rational criticism. External world criticism, like any other skepticism, insists that beliefs be given up if they become untenable. Strawson’s Humean “natural belief” is untenable by these standards.

Macarthur concludes that these representative naturalistic responses fail to stop the Humean move from naturalism (his causal theory of experience) to skepticism. Naturalism has not shown that the skeptic need not be refuted and therefore begs the question against the skeptic. So quietism on naturalist terms is not a viable solution.

Just two quick observations:

(I) Part of Macarthur’s point against (2) is that accounts for reliability are infinitely regressive. But this may not be as damaging for reliabilism as he seems to think. The accuracy of inductive reasoning may be enhanced by further induction (Popper, not Hume). Similarly, subsequent reliable processes may have corrective effects on the original process. So reliability may not be the dogmatic notion as which Macarthur portrays it.

(II) Macarthur suggests that external world skepticism withstands all these responses. However, to withstand them, it has to be modified in each case. The skepticism that survives (1) is not the same as the skepticism that survives (2). As (1) and (2) can be held jointly, naturalism might try to corner external world skepticism by combining these responses. I hope I can make this a little clearer:

To manoeuvre external world skepticism past (1), the skeptic must accept that there is some rationally justified knowledge, just not that about the external world. If positioned against (2), this appears to amount to the concession that there is some actual reliabilist knowledge – as there is rationally justified knowledge about something, though not the external world, the reliability of the process by which this knowledge is reached is confirmed as well. It does not seem impossible, then, to expand this reliable process tentatively, to close the causal gap between mind and world and to include beliefs about the external world. These cannot be not true because the process is unreliable, and this seems to hold regardless of the availability of rational justifications for them.

VRG: Maddy on Hume

The chapter on Hume (I.3) is entitled “Hume’s naturalism”. However, Maddy’s chief interest here is in Hume’s skepticism and in the connection between Hume’s skepticism and his naturalism. Her general line is that for skepticism to follow from naturalism, as is the case in (some interpretations of) Hume, this naturalism must be defective.

It is not difficult to see how this chapter connects to the previous ones. Against straightforward Cartesian skepticism, the SP maintains that an inquiry yielding reasonable beliefs can go ahead without the seal of certainty. Against extraordinary Cartesian skepticism, she maintains that an external justification of ordinary knowledge is not asked for. Humean skepticism is in line with the SP’s thinking so far. It raises cautionary rather than fundamental doubts, because it has roots in everyday empirical reasoning and does not adopt an “external” perspective on knowledge. However, Humean skepticism poses a different and more serious threat to the SP’s project. If skepticism is the “internal” consequence of an investigation based on ordinary perception and reasoning, she cannot simply undercut or ignore the skeptical challenge. In this case, the very stuff of her worldview, reasonable belief, generates doubts about rational warrants for such beliefs and thus undermines her investigation.

There are two basic ways of looking at the relation between naturalism and skepticism in Hume. Either his skepticism and his commonsense approach are distinct from each other, or his position is of one piece. The first set of accounts is less interesting. If seen as a separate issue, Hume’s skepticism can be treated more or less along the lines of the skepticism about external justification. Given the problem of an “internal” skepticism, Maddy concentrates on the single Hume for whom skepticism is a consequence of naturalism. She considers two versions of this interpretation. On the first of these (Broughton), Hume’s skepticism reflects clashes between norms of ordinary perception and reasoning. On the second of these (Stroud), Hume’s skepticism arises from his naturalistic rejection of the Cartesian ego. On the first view, there is a direct connection between Hume’s naturalism and skepticism. On the second view, this connection is indirect. It has the character of a critical appropriation, on the part of ordinary knowledge, of answers to extraordinary skepticism.

The direct connection between Hume’s naturalism and skepticism (after Broughton) can be pictured as follows. Ordinary perception and reasoning is subject to norms of clarity, consistency, carefulness, certain styles of causal argumentation and the existence of an external world. According to Hume, causal reasoning and the commitment to the existence of an external world can come apart in ordinary perception. I won’t rehearse Hume’s argument here, nor Maddy’s brief gloss on it. The familiar outcome is that ordinary reasoning can only rely on resemblance and contiguity, not cause and effect, when making connections between matters of fact. It can motivate us to attend to different ideas but falls short of reasonable beliefs. So if norms of ordinary perception and reasoning can come apart, we are left with certain habits of thought, not with stringent reasoning. This inspires cautionary skepticism.

Maddy’s SP concedes that ordinary cognitive norms can clash. Where Hume sees irrevocable confusion, however, the SP still sees potential for improvement. In her view, Hume is mistaken to conclude from the failure of some norms of ordinary perception and reasoning that they fail all at once. From the SP’s perspective, the norms of ordinary perception and reasoning are open to reassessment and refinement, much like the claims of second philosophy in general. So if there is a clash between these norms, some norms should be amended or changed. This process leaves enough ground for the SP to stand on, even if there is an incompatibility between, say, principles of causal reasoning and commonsense realism. In short, Hume’s direct “internal” skepticism can be defused by appealing to a more thoroughgoing fallibilism. According to the SP, Hume’s declaration that these clashes are irrevocable and irremediable falls short of this “spirit of open inquiry” characteristic of naturalism. So his skepticism does not follow from naturalism properly conceived, and the SP prevails.

The indirect connection between naturalism and skepticism (after Stroud) does not involve specific ordinary cognitive norms. For Hume, reasoning as such is part of the natural causal order. Hence its opposition to the detached thinking substance of Cartesian philosophy. Hume’s basic argument against the Cartesian ego is that standards of detached reasoning fail, because they do not reflect how human beings are like from an empirical perspective. If measured by the standards of detached reasoning, empirical human beliefs could never be reasonable. Clearly, the SP agrees with this critique.

But the indirect view doesn’t leave it at that. It describes Hume’s skepticism as something like an after-image of his critical engagement with the Cartesian ego. Stroud argues (in oddly dialectical fashion) that this engagement prompts the transfer into the commonsense view the traditional philosophical attitude that something is lacking from ordinary practices, turning this attitude against the traditional philosophical view. What Hume has learned from the traditional philosophical perspective, according to Stroud, is that ordinary practices can be accounted for comprehensively by distancing the account from ordinary terms. Against the detached standpoint, however, Stroud’s Hume envisages a distancing from the ordinary view that is continuous with this view. The perspective anticipated by Hume—as I understand Stroud, and I’m not sure if I get his point—is that of a sustained naturalistic investigation of human life which is a fully philosophical naturalism, a philosophical vindication, rather than a mere restatement, of ordinary perception and reasoning in the medium of that reasoning. Hume’s skepticism is an after-image of this Cartesian impulse, because Hume is kept from making sense of a comprehensive account of human nature in the medium of ordinary reasoning by his associationism. He fails to carry forward his naturalistic project, so the indirect view, because he cannot revert to a realist picture of human nature.

To the SP, the most important virtue of the indirect view is to have exposed another insufficiency in Hume’s naturalism. As before, this confirms to her that Hume’s “internal” skepticism does not follow from naturalism properly conceived and thus doesn’t present a threat to the SP’s own project. (She does not make much of Stroud’s transfer from Descartes in this context. To her, the naturalistic project of a Hume cured from his doubts would be a plain triumph over traditional philosophy.) In the concluding lines, the SP suggests how to remedy the limitations of Hume’s naturalism. An obvious course of action (already suggested by Stroud) is to fully naturalise the mental side of Hume’s views on perception and reasoning. The SP’s therapy (briefly hinted at here and presented in the second part of Maddy’s book) will replace associationism with evolutionary psychology.

Questions: Can the SP expand her fallibilism about reasonable belief to the norms of ordinary perception and reasoning without further ado? Are these norms just reasonable beliefs? Is this second order fallibilism? Either of these would be strange, or require more argument, it seems to me. Aren’t reasonable beliefs about the world revised against the background of cognitive norms as well? If new evidence forces us to revise our theory, doesn’t this involve readjusting e.g. offset explanatory models against norms of consistency rather than revising these norms?
It may be a bit unfair to make much of Maddy’s concluding gestures about evolutionary psychology. Still, given that Hume’s skepticism culminates in the claim that our reasoning is truly just a habit of association, we might wonder whether the SP’s evolutionary psychology doesn’t simply discover further habits and enshrine them as reasoning. How would this defeat skepticism?