Williamson – Philosophy of Philosophy – 7.4

Section 4 of chapter 7 in The Philosophy of Philosophy aims to identify the judgment skeptic’s mistake. In context, Williamson argued in section 3 that the same line of critique judgment skeptics use against folk theory can be used against elements of judgment skepticism that rely on folk theory. A judgment skeptic holds that we cannot know mountains exist because our evidence is neutral between the ordinary hypothesis and the skeptical hypothesis. Instead, there are only micro-events that humans errantly, though conveniently, classify as mountains. The result, however, is that we cannot possess knowledge or justification about beliefs concerning mountains. When this kind of reasoning is ported over to general skepticism it become clear (according to Williamson) that the reasoning is unsound. With the context of section 3 in mind I return to section 4. Williamson wants to identify the mistake in the judgment skeptic’s reasoning. What makes this line of reasoning bad?

There are two mistakes that Williamson identifies. The first mistake is the use of so-called appearance principles, and the second mistake is committing the consequence fallacy. I will discuss each of these mistakes in turn.

An appearance principle is defined as follows:

[O]ne should be confident that P (on the basis of common sense) only if its appearing (by the standards of common sense) that P is good evidence that P. (2007: 227)

Williamson shows that appearance principles can be used as premises in an argument for general skepticism as well as judgment skepticism. This is a problem because judgment skeptics want to exclude the results of particle physics from skepticism so that they can claim underlying micro-physical events entail the impossibility of mountains. I will provide you with an overview of Williamson’s argument.

Let SS be the judgment skeptic’s scenario in which there are no mountains. In this scenario it falsely appears that there are mountains even though mountains are a metaphysical impossibility. If there really are mountains, then SS must not obtain. For the judgment skeptic: one should be confident that SS does not obtain only if its appearing that SS does not obtain is good evidence that SS does not obtain. However, appearing that SS does not obtain is not good evidence that SS does not obtain, according to the judgment skeptic, so one should have low confidence (in one’s judgment) that SS does not obtain. Now, I turn to a distinction.

Roughly, something is truth-indicative if the appearance of it raises the probability of P. If, on the other hand, appearance (used as a conditional on P) does not raise the probability of P above the probability of P alone, then appearance is falsity-indicative. Appearance principles require one to modulate one’s confidence in P according to how appearance that P provides evidence that P, and only if the appearance of P is truth-indicative should one be highly confident in P.

The use of appearance principles in the reasoning above can also generate general skepticism. Let p be a description of the external world that jives with the judgment skeptic’s understanding of particle physics. Imagine SS* is an evil demon scenario in which p is false but an evil demon makes the truth of p seem to hold. By the same reasoning, the appearance that SS* does not obtain is not evidence that SS* does not obtain (i.e., it is not truth-indicative) because appearances to a subject are systematically deceived by the demon. So, given the appearance principle, one should have low confidence that SS* does not obtain. Because p (the existence of the external world) entails that SS* does not obtain, then one should modulate one’s confidence in p to accord with one’s confidence that SS* does not obtain. The result is that confidence in p should be low even when its appearance raises the probability of p. So, we should be skeptical about the existence of the external world as described by particle physics. Williamson cuts the legs out from under the judgment skeptic’s reasoning. Or, does he?

I’m not satisfied with Williamson’s pattern of pulling the judgment skeptic into general skepticism. Why? The mere possibility of an evil demon scenario precludes the use of appearance principles. In such a scenario appearances are false and, consequently, apperance principles do not hold. Who would reasonably argue that in a Matrix world one should be confident that P only if it appears that P is good evidence that P? By the assumptions of the scenario it appearing that P will not be good evidence that P. So, to argue that appearance principles used in such a scenario result in skepticism about a domain judgment skeptics endorse (particle physics) seems like a ticky-tacky move at best and unwarranted at worst.

The second mistake in judgment skepticism is the consequence fallacy. This fallacy involves criticizing confidence in a theory by focusing on a logical consequence of the theory whose probability is not raised by the evidence. Take the following argument Williamson outlines (2007: 233):

  1. Physical events occur that folk geography takes to constitute the presence of mountains in Switzerland.
  2. If physical events occur that folk geography takes to constitutes the presence of mountains in Switzerland, then there are mountains in Switzerland.
  3. There are mountains in Switzerland.

A person who subscribes to folk geography is likely to endorses the whole argument. However, a judgment skeptic jumps off the boat at premise 2. That is, the evidence may increase the probability of premise 1 but not premise 2. The fallacy comes from arguing that the failure of increased probability in 2, conditional on the evidence, is reason to hold that a high degree of confidence in both 2 and 3 is not warranted. It may be that it is still reasonable to hold a high degree of confidence in 2 and 3 even though evidence raises the probability of 1 but not of 2. The problem comes from, “identifying a logical consequence of the theory (not itself a logical truth) whose probability is not raised by the evidence” (2007:232). It is not the case that evidence raising the probability of a hypothesis makes more probable a logical consequence of that hypothesis. In fact, according to Williamson, when the evidence makes the hypothesis more probable, but not certain, it decreases the probability of the logical consequence of the hypothesis. When evidence makes a hypothesis certain it does not make a logical consequence of that hypothesis more probable. Thus, evidence making more probable premise 1 but not 2 is not a basis from which to argue that one is not entitled to a high degree of confidence in premise 2 and 3.

Williamson’s logical consequence point brings up issues in confirmation theory. His point has prompted me to explore confirmation theory in more detail. Some useful reads in this regard can be found here and here.


Add yours →

  1. Hi Chris. Can a confirmation theory possibly be used to support the Gospel,the existence of God, or the validity-accuracy-and divine accuracy of the Bible to a non-believer? By “divine accuracy”, I mean that the original writers didn’t exaggerate the stories from the start.

    • Hi Scott…Interesting question. There are a couple of issues at play. The first question might be, “Is it possible to generate consensus around what counts as ‘neutral’ evidence?” If, like Williamson, consensus around the truth-value of evidence is required for something to count as neutral evidence, then it will be difficult to persuade a non-theist to endorse the hypothesis “God exists.” In a recent paper (“Williamson on Evidence Neutrality”) I tried to revise what is known as the ‘Evidence Neutrality’ thesis so that it is possible for people in two different camps to agree over what constitutes evidence for the hypothesis. This challenges people to temporarily set aside their beliefs and ask, for instance, “If there is evidence that a miracle occurred (whatever that evidence might look like), then that evidence would support the existence of God to X degree.” This is to engage in counterfactual reasoning about what kind of evidence would count as supporting the hypothesis and to what degree it would support the hypothesis. Without achieving consensus around what counts as ‘relevant’ evidence from the start you will be talking past a non-theist. Using, for example, the Bible as a source of divine authority that proves the existence of God (his character, his power) is futile unless you can agree with the non-theist that proof of the divine inspiration of the Bible would count as evidence confirming the hypothesis that God exists. This pushes the debate back to the evidence for your evidence. Now the debate is focused on the foundations of the evidence (i.e., the historical reliability of the old and new testament). Is the Bible a series of exaggerated stories or is it an accurate reflection of who God is?

      On Williamson’s account, a non-theist will say the bible is false and a theist will say it is true, and, as a result, it cannot be admitted as neutral evidence for the hypothesis that God exists…end of story. My methodology opens up greater room for debate and consensus around the evidence admitted for the inquiry. This works to build bridges between the inquirers instead of endlessly using evidence the other party cannot see as relevant. Without going through this process you merely beg the question against the non-theist: using a piece of evidence in dispute to try and prove the thing you are trying to prove; that is, assuming what you are trying to prove by using the Bible (as divinely-inspired authority) as evidence for what you are trying to prove (the existence of God). This is where the second issue comes into play and where your question might take bite.

      Using confirmation theory to prove the existence of God or the divine authority of the Bible might be an interesting way of proceeding. Instead of trying to produce logical certainty in an argument for God’s existence, another option is to proceed probabilistically and produce a proof-of-evidence argument supporting the hypothesis. This gets into issues in inductive logic and confirmation theory, but I see no reason why confirmation theory could not inform a probabilistic argument for the existence of God. Developing the argument would prove fruitful. Perhaps I will attempt such an argument in another post.

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