Chapter 4: Skepticism

Let me continue with my book summary.

I come to my favourite chapter of the book, the chapter on skepticism. This chapter completes the triad of what Fogelin calls “the trinity of threats to our rational lives: inconsistency, illusion, and doubt.” It presents the view that skepticism “grows naturally out of the epistemological project” by looking at cartesian skepticism (smallcase for “cartesian” because Descartes was an antiskeptic), Hume’s problem of induction and Pyrrhonian skepticism. The conclusion is “Unrestricted philosophizing itself generates all these skeptical challenges and…meets none of them”.

A brief summary of these three forms of skepticism follow.

cartesian skepticism

The Meditations on First Philosophy is where Descartes uses his famous “malicious demon” thought experiment to discover what knowledge, if any, can be acquired from indubitable foundations (the idea is that if something can be true under the following scenario, then it must be indubitable):

...suppose…that…some malicious demon of the utmost power and cunning has employed all his energies in order to decieve me. I shall think that the sky, the air, the earth, colours, shapes, sounds and all external things are merely the delusions of dreams which he has devised to ensnare my judgement. I shal consider myself as not having hands or eyes, or flesh, or blood or senses but as falsely believing that I have all these things. I shall stubbornly and firmly persist in this meditation; and, even if it is not in my power to know any truth, I shall at least do what is in my power, that is, resolutely guard against assenting to any falsehoods, so that the deceiver, however powerful and cunning he may be, will be unable to impose on me in the slightest degree.

From First Meditation of Meditations on First Philosophy translated by John Cottingham. (John Veitch translation here. Elizabeth Haldane’s translation here.)

The modern variant of Descartes’ malicious demon thought experiment is the Brains in a Vat scenario. The challenge is to prove that we are neither brains in vats nor deceived by a malicious demon. How do we justify our everyday beliefs that the skeptical scenarios presented are false?

Humean Skepticism (aka the problem of induction)

The problem of induction is (crudely) this: Deduction and induction are the only two ways of reasoning available to us. Induction is not deduction. Induction cannot justify induction. So, we cannot justify our reliance on induction.

Fogelin quotes from Hume’s Abstract of A Treatise of Human Nature.

...all reasonings concerning cause and effect are founded on experience, and … all reasonings from experience are founded on the supposition that the course of nature will continue uniformly the same. We conclude that like causes, in like circumstances, will always produce like effects. It may now be worth while to consider what determines us to form a conclusion of such infinite consequence.

It is evident that Adam, with all his science, would never have been able to demonstrate that the course of nature must continue uniformly the same, and that the future must be conformable to the past. What is possible can never be demonstrated to be false; and it is possible the course of nature may change, since we can conceive such a change. Nay, I will go farther, and assert that he could not so much as prove by any probable arguments that the future must be conformable to the past. All probable arguments are built on the supposition that there is this conformity betwixt the future and the past, and therefore can never prove it. This conformity is a matter of fact, and, if it must be proved, will admit of no proof but from experience. But our experience in the past can be a proof of nothing for the future, but upon a supposition that there is a resemblance betwixt them. This, therefore, is a point which can admit of no proof at all, and which we take for granted without any proof.

Also see section IV of Hume’s Enquiry Concerning the Human Understanding.

For other Hume texts, click here.

Pyrrhonian Skepticism
The last form of skepticism Fogelin discusses is Pyrrhonian Skepticism, after Pyrrho of Ellis (360-270 B.C). Little is known about Pyrrho. However, the type of skepticism associated with Pyrrho has been summarised and codified by Sextus Empiricus in his Outlines of Pyrrhonism.

According to Fogelin, Pyrrhonian skepticism is an example of belief skepticism, as opposed to cartesian and Humean skepticism, which both fall under justification skepticism. Pyrrhonian skepticism aims at peace of mind through eliminating philosophical commitment. The way to go about eliminating philosophical commitment is to suspend our beliefs and the Pyrrhonian method for suspending belief is to apply the Five Modes of Agrippa to any argument that leads to a philosophical commitment.

A Stanford Encyclopedia article on Ancient Skepticism describes the Five Modes as follows

The five modes of Agrippa (whose date is unknown, though he is later than Aenesidemus) focus, as Barnes has shown, on some of the underlying epistemological concerns that motivate skeptical conclusions. Sextus presents them at PH 1.164-77, where he says that they promote the suspension of judgment by invoking:

— disagreement, for among philosophers and ordinary people there is interminable disagreement; — regress ad infinitum, for the skeptic asks for a proof of a claim, a proof of the reliability of this proof, and so on ad infinitum; — relativity, for things are relative to both one’s subjective nature and the concepts one employs in judging them; — hypothesis, for the skeptic does not allow us to take as our starting point something which is taken for granted; — circular reasoning, for the skeptic rejects proofs that are circular, as when sense impressions are used to establish the veracity of the senses.

Another summary on the Five Modes of Agrippa from the Internet Encyclopedia of Philsophy on Ancient Greek Skepticism:

Agrippa’s Five Modes relies on the prevalence of dispute and repeats the main theme of Aenesidemus’ Modes: we are frequently faced with dissenting opinions regarding the same matter and yet we have no adequate grounds on which to prefer one view over another. Should a dogmatist offer an account of such grounds, the skeptic may then request further justification, thereby setting off an infinite regress. And presumably, we should not be willing to accept an explanation that is never complete, i.e. one that requires further explaining itself. Should the dogmatist try to put a stop to the regress by means of a hypothesis, the skeptic will refuse to accept the claim without proof, perhaps citing alternative, incompatible hypotheses. And finally, the skeptic will refuse to allow the dogmatist to support his explanation by what he is supposed to be explaining, disallowing any circular reasoning. And of course the skeptic may also avail himself of the observation that what is being explained only appears as it does relative to some relevant conditions, and thus, contrary to the dogmatist’s presumption, there is no one thing to be explained in the first place.

As an example of the Five Modes in action, Fogelin gives this example:

To test this claim that the Pyrrhonian skeptic does not dogmatize, we can consider perhaps the best-known maneuver in thePyrrhonian corpus, the treatment of the criterion of truth. The Stoic epistemologists held that to judge correctly, one must be in possession of a proper criterion of truth – a test that provides invincible evidence for the truth of some belief. Presented with such a claim, the Pyrrhonian skeptic proceeds hypothetically by assuming that the dogmatist is correct in demanding a correct criterion of truth and then dranws out the consequences of this demand. The Pyrrhonist presents his dogmatic opponent with the following argument: If someone presents a criterion of turh, then it will be important to determine whether is the correct criterion. There is, after all, disagreement concerning which, if any, criterion is the correct criterion of truth. If the stated criterion is siad to be correct without the employment of a criterion of truth, then it must either be the same criterion or a different one. If the same criterion of truth is used for judging the criterion of truth, then the defense of the criterion will be question-begging. If a new criterion of truth is used, then the challenge is repeated, ad infinitum if necessary. Thus, the dual demons of circularity and infinite regress are let loose as soon as the Stoics attempt to defend their choice of a criterion of truth. If they refuse to defend it, then they have simply abandoned their idea that all judgments must be made in conformity with a correct criterion of truth.

Peter Suber sums it up brilliantly here:

But here we encounter a classical and recurring skeptical dilemma. Either our one criterion certifies itself, which is circular, or a second criterion certifies the first, in which case we will need a third to certify the second, and so on ad infinitum. So it seems we must either beg the question or fall into an infinite regress.

Nothing is left except to forgo all support and simply claim (stipulate or hypothesize) that the criterion is a good one. But others will do the same for different criteria, on equal authority, and the resulting disagreement will be final, clearly equipollent, and ripe for suspended judgment. If the criterion is affirmed hypothetically, just to see where it goes and how it works, then all the statements it validates as a criterion will be equally hypothetical.

Or the criterion may be tested by its fruits. If it validates certain statements and not others, then we will say it is a good criterion. But this is just another way to beg the question, for it presupposes what is to be proven, namely, that we know which statements are true, or that the criterion is good and validates only true statements. Or again, this is to use the resulting statements as the criteria, and the problem reappears.

So it seems that a criterion is not supported at all, or is supported by circular reasoning or by an infinite regress. In any case its support is inadequate for genuine certainty about the criterion. In particular, other criteria could always be proposed with equipollent support. Then suspension of judgment on which, if any, is the true criterion would be required by honesty.

But if no criterion is ever certain, then no statement is ever certain, for statements are made certain by supporting arguments or evidence, which are discerned by virtue of a criterion. Of course even this claim is uncertain.

Then there is the paradox of proof. An alleged proof may be valid according to some given rules of valid reasoning —and skeptics have attacks on all rules of validity, in general and in particular— but its conclusion is only demonstrably true if its premises are true. But we only know that the premises are true if they themselves are proven. Clearly we are again entangled in the dilemma of circular reasoning and infinite regress. If we prove the premises, then their proof will have its own premises that need proof, and we are committed to an infinite regress of proofs that we can never supply. The result is that nothing is ever proved with finality. If unproved premises can make good proofs, then we can invent unproved premises from which we could derive any proposition whatsoever, thereby putting all possible conclusions into isosthenia.

Fogelin suggests that we land ourselves in such trouble because we raise the level of scrutiny without any good reason to do so. But this claim is of course open to skeptical doubt, using the Five Modes presented above! No wonder Hume called sceptical doubt a “malady”!

This is probably my last post on the book. It’s not a full summary of Fogelin’s book, only the parts that I found most interesting and wanted to share.

Thank God. Finally, got this post over and done with. Good riddance!