Underdetermination Skepticismand Skeptical-Dogmatism

Abstract

The Mundane World Hypothesis (MWH) says that we have material bodies, we have brains located inside our bodies, we have sense organs which process visual information, the direct cause of our perceptual judgments is typically macroscopic material objects, and we live in a material world. Skeptics using underdetermination arguments argue MWH has no more epistemic merit than some skeptical competitor, e.g., that we are in the Matrix. Such competitor hypotheses are equipollent so, we are not justified in believing MWH. This paper takes the underdetermination skeptic’s premises to a more radical conclusion: skeptical-dogmatism, which is the view that MWH is probably false based on the idea that there are many equipollent competitors to MWH.

1.Introductory

Underdetermination arguments for skepticism about the external world turn on the claim that evidence for belief in the external world hypothesis is no better than some skeptical competitor hypothesis, e.g., the hypothesis we are trapped in a virtual reality like the Matrix. Since evidence does not favor the one hypothesis over the other, we have good reason to believe that we are not justified in believing in the external world.[1]The historical antagonistsare dogmatists who claimwe have justified belief in the external world hypothesis. The main aim of the paper is to show that the usual underdetermination considerations advanced in favor of skepticism about the external world actually support a stronger conclusion, namely: we are justified in disbelieving the external world hypothesis, since it is probably false.[2] We will call this position ‘skeptical-dogmatism’.[3] It sides with the dogmatist in saying that a suspension of judgment is not warranted, and it sides with the skeptic in saying that a positive verdict about knowledge or rational belief in the external world is not warranted.

A subsidiary aim is to show that skeptical-dogmatism provides its own unique challenges to dogmatism. In part, this is because at least one of the premises supporting skeptical-dogmatism is weaker than the corresponding premise in typical underdetermination arguments for skepticism. Furthermore, the stronger conclusion of skeptical-dogmatism also means that at least some (unmodified) dogmatic responsesto underdetermination skepticism, including many forms of externalism, will not work against dogmatic-skepticism.

2.A Tale of Two Professors and One Student

This section will illustrate the general contours of the argument with a tall tale. Subsequent sections will develop and defend various parts of the informal version of the argument.

Imagine Illustrious University offers two sections of epistemology. Fickle, a philosophy major, signs up for both sections with the aim of dropping one course and taking the section with the better professor (meaning the professor with fewer course requirements). In Professor Relic’s class, Fickle learns about underdetermination arguments for skepticism and their venerable history dating back to the Ancient Greeks. Relic, blissfully unaware of his soporific powers, quotes Sextus Empericus to the class:

The Skeptic Way is a disposition to oppose phenomena and noumena to one another in any way whatever, the result that, owing to the equipollence among the things and the statements thus opposed, we are brought first to epochè and then to ataraxia. …At this point we are taking as phenomena the objects of sense perception, thus contrasting them with the noumena…By “equipollence” we mean equality as regards credibility and the lack of it, that is, that no one of the inconsistent statements takes precedence over any other as being more credible. Epochè is a state of the intellect on account of which we neither deny nor affirm anything. (Mates 1996, 8-10)

Professor Relic points out that the idiom of ‘equipollence’ is somewhat antiquated, but the underlying idea that we should suspend judgment when a belief lacks greater probability than some competitor is familiar enough. A typical example is this: The police know the criminal worked alone(A. H. Goldman 2007). They have amassed evidence that equally supports the hypothesis that Bill committed the crime, and the hypothesis that Phil committed the crime. The temptation to say that we ought to suspend judgment about the innocence or guilt of Bill and Phil is clear. The Pyrrhonians thought such suspension would induce a state of “quietude” (ataraxia).

Professor Relic asks the class to apply underdetermination thinking to whether our belief in the external world is justified. He is quick to point out that the expression ‘the external world’ is a bit unfortunate as it might seem to suggest that to overcome skepticism about the external world one need only demonstrate justified belief in something external to one’s self. On this understanding, it seems that a world with just you and Descartes’ evil demon will count as one where there is an external world. However, ‘the external world’is often thought to refer to something more specific like the Mundane World Hypothesis (MWH). MWH holds, among other things,that (i) we have material bodies, (ii) we have brains located inside our bodies, and (iii) we have sense organs that process visual information. Furthermore, (iv) the direct cause of our perceptual judgments is typically macroscopic material objects and (v) we live in a material world. In addition, (vi) our epistemic relationship to the world is autonomous: evil demons, advanced aliens and so on, do not get involved in our epistemic lives. Professor Relic points out that MWH is rather unremarkable: common sense, science and naturalized epistemology agree in the main about MWH.[4]

Professor Relic notes effects can often have many different causes. A house fire can be started by an electrical fault, grease spilling on a stove burner, smoking in bed, arson, etc. Similarly, there are many possible causes for our sensory experience. He asks the class to consider Berkeley’s competitor hypothesis. Berkeley agrees that we directly see macroscopic objects, tables, trees, teacups, etc., but adds that we perceive only ideas, so macroscopic objects are ideas (Winkler 1989, 138). When asked what evidence might be offered in favor of the MWH over Berkeley’s World Hypothesis (SH2) the class (under a bit of dialectical pressure) is quickly stymied. Relic points out that any such evidence would have to be either a priori or empirical. He argues:

(i)We have no a priori access about the nature of the causes of our experiences which favors MWH.

(ii)We have no empirical access to the nature of the causes of our sensory experiences that favor MWH, since subjectively, our experience would be indistinguishable if SH2 is true.[5]

Professor Relic, with triumphant glee, concludes that MWH is underdetermined: we are not justified in believing MWH because it has no more going for it, evidentially speaking, than Berkeley’s hypothesis. That is, since P(MWH/e) = P(SH2/e), where ‘e’ is the evidence available, we are not justified in believing MWH.

Fickle hears almost the same lecture in his other epistemology class except Professor Nouveau uses the hypothesis associated with the Matrix movie (SH1) instead of Berkeley’s hypothesis. (Professor Nouveau hopes that the appeal to the Matrix movie is more interesting for his students and they will reward him come student satisfaction survey time). Not surprisingly then, Professor Nouveau, with triumphant glee, concludes that MWH is underdetermined: we are not justified in believing MWH because it has no more going for it, evidentially speaking, than the Matrix hypothesis. That is, since P(MWH/e) = P(SH1/e), we are not justified in believing MWH.

Perhaps the most farfetched aspect of our story is that some university might offer two sections of epistemology by two different professors in the same term. Other than that, I take it that the rest of the tall tale is pretty standard stuff. The professors’presentation of the underdetermination argument is familiar enough. True, theydiffer in their choice of examples of competitor hypotheses, but this too is not uncommon.[6] I suspect the Matrix moviemade it easy for some epistemologists to retire the brain-in-a-vat hypothesis. Perhaps the movie Inception made it possible for some professors to retire the Matrix hypothesis. Certainly it would make sense to discuss underdetermination with respect to either of these movies in a philosophy of film class, while a professor teaching modern philosophy would have good reason to follow Relic in using Berkeley’s hypothesis to illustrate underdetermination skepticism. In short, I think it is quite plausible to assume that it is not uncommon to present underdetermination arguments using different skeptical hypotheses to illustrate the argument.

Now for the rest of our tall tale: Fickle finds himself in the ironical position of finding equipollent the question of which section of epistemology to drop. It seems both professors have assigned large workloads and both seem equally incompetent. He decides to stick with the two classes for one more week. The following week, Fickle points out to Professor Relic that Professor Nouveau argued in his class that P(MWH/e) = P(SH1/e). Professor Relic agrees that this is correct. He could just as easily have used the Matrix hypothesis to illustrate the point (but he has no need to fawn for high student evaluations because he has tenure). Similarly, Fickle points out to Professor Nouveau that Professor Relic argued that P(MWH/e) = P(SH2/e). Professor Nouveau agrees that this is correct. He could just as easily have used Berkeley’s hypothesis (but then he would be a fuddy-duddy, like Professor Relic).

Fickle asks his professors about whether SH1 is identical with SH2. Both professors agree that SH1 ≠ SH2. Indeed, they are competitors in just the same way that each is a competitor to MWH. Fickle inquires further whether evidence favors SH1 over SH2 or vice versa. The professors agree that evidence does not favor the one over the other: there is no a priori reason to prefer one over the other, and subjectively, one could not distinguish on the basis of sensory evidence, SH1 over SH2 or vice versa. So the two professors agree that P(SH1/e) = P(SH2/e). But then there is an obvious problem in claiming that we should neither affirm nor deny MWH. For if P(MWH/e) = P(SH1/e) and P(MWH/e) = P(PSH2/e) and P(SH1/e) = P(SH2/e), then the maximum epistemic probability of MWH is 0.33. Indeed, transitivity and the assumption that SH1 ≠ SH2 leads to the same conclusion. Forif P(MWH/e) = P(SH1/e), and P(MWH/e) = P(SH2/e), then P(MWH/e) = P(SH1/e) = P(SH2/e). In which case, again,the maximum epistemic probability of MWH is 0.33. Fickle suggests that by the professors’ own premises it appears we are in a position to say MWH is probably false. Fickle then asks each professor how this supports the Pyrrhonian idea that we should “neither deny nor affirm anything,”since saying that MWH is probably false is surely one way to deny MWH, and so epochè about the external world is thwarted. Fickle has arrived at skeptical-dogmatism.

3.Ten Skeptical Hypotheses

In what follows, I shall try to spell out and defend the argument. Again, however, I shall not attempt to defend the usual premises of the underdetermination argument, but rather, the dialectical strategy will be to assume the usual premises of underdetermination arguments against knowledge of the external world and see where they lead.[7]

One important idea that skeptical-dogmatism adds is that of multiple competitor hypotheses. This difference is significant since underdetermination arguments are typically formulated in terms of a single competitor.[8]The minimum the argument for radical underdetermination of MWH requires is two competitors. Clearly, however, there is any number of competitors to MWH. Here are a few, including some of the most discussed:

SH1: I am in the “Matrix”. I have a body. I live in a virtual reality constructed by an advanced computer system that interfaces with my brain.

SH2: Berkeley was right that there are only minds and ideas; there is no material world.

SH3: I am in an “Inception” dream: a dream manipulated by others for the purposes of extracting information.

SH4: I am a brain-in-a-vat. I lack a body. I live in a virtual reality controlled by an advanced computer system that interfaces with my brain.

SH5: I am deceived by Descartes’ evil demon.

We can easily create more. And so, in deference to cultural skeptical diversity, let us suppose:

SH6: I am deceived by Anhaka (Hindi demon).

SH7: I am deceived by Bushyasta (Zoroastrianism demon).

Other skeptical possibilities include:

SH8: There is a material world, but we are brains-in-a-vat held in an underground laboratory by a mad scientist. Our bodies are robots that walk the earth. Information is sent between the robots and our brains in the underground laboratory via radio waves.

SH9: There is a material world, but we are brains-in-a-vat held in an underground laboratory by a mad scientist. Our organic bodies are brainless zombies but nevertheless, they walk the earth. Information is sent between our bodies and our envatted brains via radio waves.

SH10: We are purely electronic beings living in a computer simulation of the MWH.

MWH is incompatible with each of SH1-10. Indeed, we should understand all eleven hypotheses as logical contraries: in any pairwise comparison, both may be false but both cannot be true.[9]

Not only have a number of competitors to MWH been discussed in the literature, but the fact that MWH makes a number of claims about reality (described by Relic in (i) to (vi) above) gives us good reason to think that MWH has multiple competitors. After all, denying one conjunct of (i) to (vi) is sufficient to deny MWH, so this fact alone opens up the possibility of multiple competitors to MWH. We shall return to this point below in more detail.

4.Underdetermination and Radical Underdetermination Principles

As noted, underdetermination principles are typically formulated in terms of a single competitor. A characteristic formulation is provided by Hazlett:

U2: Underdetermination Justificatory Principle (UJP): “Ifh1andh2are hypotheses ande is all S’s evidence, S is justifiedin believingh1only if P(h1/e) > P(h2/e) (2006, 200).”

It will be convenient to use Hazlett’s formulation in what follows, but it is worth saying something about different formulations of the underdetermination principle. The following comes from Jonathan Vogel:

UP1: “If q is a competitor to p, then a subject S can know p only if p has more epistemic merit (for S) than q(2005, 73).”

Duncan Pritchard offers:

UP2: “For all S, p, q, if S’s evidence for believing p does not favour p over some hypothesis q which S knows to be incompatible with p, then S’s evidence does not justify S in believing in p (2005b, 39).”[10]

To say that q is a competitor or incompatible with p is typically understood, as noted above, as implying that they are logical contraries: if q is true, then p is false. What is the relation between these two? UP1 seems weaker as it does not rule out the possibility that S may have a justified belief in p, only that the justification is insufficient for knowledge. Conversely, UP2 implies that p is not known when evidence does not favor it (on the assumption that justification is necessary for knowledge). For ease of exposition we will focus on UP2: nothing of substance hangs on the potential gap between justified belief and knowledge in the present context.[11]

At first blush, the connection between epistemic merit mentioned in Vogel’s formulation and favoring in Pritchard’s formulation, and the underdetermination skeptic’s claim that our belief in the MWH is not justified, may seem puzzling. After all, it seems that sometimes epistemic merit or favoring may have little to do with justification or truth. A model showing the sun as the center of the solar system may have the epistemic merit of (or have in its favor) increased student understanding, but strictly speaking, it is false according to our best physics. To avoid such worries it will be helpful to directly connect the notions of ‘epistemic merit’ and ‘favoring’ in terms of epistemic probabilities. One connection can be made via the translation principle. Let ‘e’ be the total sensory and non-sensory evidence available to some subject S:

Translation Principle: If h1 has more epistemic merit than h2 for S, or S’s evidence (e) favors h1 over h2, then P(h1/e) > P(h2/e) for S.

The translation principle allows us to go from UP2 to U2, which, as noted, we will employ in subsequent discussion.

To allow for multiple competitors, think of ‘radical underdetermination’ as the situation where there are two or more competitor beliefs or hypotheses and think of ‘run-of-the-mill underdetermination’ (hereafter just ‘underdetermination’) as having a single competitor to some belief or hypothesis.[12] We will define radical underdetermination in terms of two competitors, but this is a minimum which we will use simply for illustrative purposes. The number of competitors can be multiplied without limit.

RU2: Radical Underdetermination Justificatory Principle (RUJP): Ifh2 and h3are competitor hypotheses to h1, ande is all S’s evidence, S is justifiedin believingh1only if P(h1/e) > P(h2/e) and P(h1/e) > P(h3/e).

Articulating RUJP in terms ofthe legal illustration, the belief that Bill is guilty is not justified if the evidence equally points to two other suspects, Phil and Dill. It is clear that RUJP isweaker than UJP. Other things being equal, the justification for believing that Bill is guilty when there is only one other suspect is greater than the justification for believing that Bill is guilty when there are two other suspects equally incriminated by the evidence. So, if one thinks that UJP provides a necessary condition for justified belief, as obviously the underdetermination skeptic must, then one should think the same of RUJP.

It is worth noting the maximum epistemic probability permitted by RUJP. If H1 does not have more epistemic merit than either of its competitors H2 and H3, then the maximum probability of H1 is one third of the total probability, that is, (approximately) 0.33.[13] For suppose H1 had a higher probability, say 0.5, as in the underdetermination illustration above. This would mean that the other two competitors would have only 0.5 epistemic probability to divide amongst themselves, and so the two competitors would then have an average probability of only 0.25, in which case we would have good reason to suppose that H1 is not radically underdetermined.

5.Underdetermination Vs. Radical Underdetermination Arguments

Underdetermination arguments for external world skepticism are typically expounded as comprising a major and minor premise.

U1: S’s evidence for believing MWH is not greater than S’s evidence for believing SH2.

U2: Underdetermination Justificatory Principle (UJP): “Ifh1andh2are hypotheses ande is all S’s evidence, S is justifiedin believingh1only if P(h1/e) > P(h2/e) (Hazlett 2006, 200).”