Lecture Supplement on Peter Unger’s “A Defense of Skepticism” 
Copyright © 2013 Bruce W. Hauptli
Unger maintains that philosophers “...think skepticism interesting only as a formal challenge to which positive accounts of our common-sense knowledge are the gratifying responses.” He disagrees, and he offers a defense of skepticism based upon a discussion of what he calls “absolute terms”—terms which apply without qualification. According to Unger, terms like ‘flat’ and ‘certain’ are basic absolute terms (they are defined by appealing to relative terms negatively—a surface is flat, for example, if it is “not at all bumpy). Moreover, he contends that these terms are non-referential and non-descriptive.
Unger claims that knowledge requires certainty, and that there is nothing we can be certain of since some doubt is always possible.
2. The Text:
324 ...every human being knows, at best, hardly anything to be so.
325 Absolute terms: ‘flat’, ‘certain’.
-basic absolute terms (e.g., ‘line’)—used to define others, and
-derived absolute terms (e.g., ‘cube’)—defined by others.
A. Sophisticated Worries About What Skepticism Requires:
(a) Some believe that skepticism implies that we hold false beliefs and such beliefs should lead us to error systematically.
-while one might lack knowledge but believe one has it (thus having a false belief), this need not lead one into a clash with reality. False beliefs need not “conflict” with our experience—if we believe a region of space is a vacuum, and it actually has a trace amount of a gas, this need not lead to a conflict between our belief and our experience.
(b) Some believe that “if skepticism is right, then the terms of knowledge, unlike other terms of our language, will never or hardly ever, be used to make simply, positive assertion that are true. In other words, skepticism will require the terms of knowledge to be isolated freaks of our language.” The remainder of the article replies to this worry by claiming that all absolute terms share the property of being [largely] non-referential!
B. Absolute and Relative Terms:
Basic absolute terms (like ‘straight’ and ‘flat’) are not defined in terms of other absolute terms. ‘Cube’, on the other hand is defined in terms of other absolute terms.
-Note that we never say that something is “nearly bumpy” though we do speak of things being “nearly flat.”
-...every basic absolute term, and so every absolute term whatever, may be defined, at least partially, by means of certain relative terms. The defining conditions presented by means of the relative terms are negative ones; they say what the relative term purports to denote is not present at all, or in the least, where the absolute term correctly applies. Thus, these negative conditions are logically necessary ones for basic absolute terms, and so for absolute terms which are defined by means of the basic ones.
-in noting these demanding negative relative requirements, we may begin to appreciate, I think, that a variety of absolute terms, if not all of them, might be quite troublesome to apply, perhaps even failing consistently in application to real things.
C. On Certainty And Related Terms:
‘Certain’ is an absolute term:
-‘It is certain that p’ =df= ‘It is not at all doubtful that p’.
-Modifiers to ‘certain’ lessen its force (e.g., ‘more certain than’).
D. The Doubtful Applicability of Some Absolute Terms:
Consider ‘flat’—does it apply to things in the world?
-...what follows from my account of “flat” is this: that as a matter of logical necessity, if a surface is flat, then there never is any surface which is flatter than it is.
-It is at least somewhat doubtful, then, that “flat” ever applies to actual physical objects or to their surfaces. And the thought must strike us that if “flat” has no such application, this must be due in part to the fact that “flat” is an absolute term.
--Philosophical aside: note that we must be careful about ‘refer’ here—“Does ‘triangle’ refer?’ vs. “Does ‘triangle’ refer to things in the physical world?”
Similarly, he contends, for ‘certain’!
-...if someone is certain of something, then there never is anything of which he is more certain.
--Are people certain that 45+56=101? Is there nothing they are more certain of?
--Are people certain there are automobiles? Is there nothing they are more certain of?
---Philosophical aside: is his analogy between ‘flat’ and ‘certain’ a fair one here? That is, ‘flat’ vs. ‘geometrically flat’ and ‘certain’ vs. ‘philosophically certain’.
E. Does Knowing Require Being Certain?
Some philosophers (e.g. Moore) say that knowledge requires certainty. Others deny this. To those who agree with Unger (and Moore) that knowledge requires certainty, Unger’s skeptical argument is now complete. Unger, however, responds to those who reject this thesis as follows:
-“In everyday affairs we often speak loosely, charitably, and casually; we tend to let what we say pass as being true. I want to suggest that it is by being wrongly serious about this casual talk that philosophers (myself included) have come to think it rather easy to know things to be so.:
--Students who “know that the battle of Hastings was fought in 1066,” but are not certain of this.
-Unger uses an example about definite descriptions [the-so-and-so] to support the need to pay attention to the way in which words are used:
--“Nelson Rockefeller is the son of John D. Rockefeller, Jr.” Note the definite description, and the uniqueness claim. Then note the “queerness” of the following statement:
--”Nelson Rockefeller is actually the son of John D. Rockefeller, Jr., and so is Winthrop Rockefeller.” Unger maintains that “...we cannot help but feel that what is asserted is inconsistent. And, with this, we feel differently about the original remark....”
Unger then applies this demand for care in using words to the issue of whether or not knowledge requires certainty. According to him, to say “He knows that it is raining, but he isn’t certain of it” is to utter an inconsistent statement:
“...while we might feel nothing contradictory at first...we would feel differently about our saying “He really knows that it is raining, but he isn’t certain of it.” And, if anything, this feeling of contradiction is only enhanced when we further emphasize, “He really knows that it is raining, but he isn’t actually certain of it.” Thus it is plausible to suppose that what we said at first is actually inconsistent, and so that knowing does require being certain.”
-Philosophical aside: as noted above, we need to distinguish between “Knowledge requires certainty” and “Knowledge requires philosophical certainty.” That is, between no plausible way of one’s claims being wrong, and one’s claims being indubitable (immune to doubt—whether plausible or implausible, possible or impossible, conceivable or inconceivable); or incorrigible (immune to calls for correction); or infallible (immune to error). In his “Varieties of Privileged Access,” William Alston maintains that there are three senses of ‘indubitable’: “...logical impossibility of entertaining a doubt, psychological impossibility of entertaining a doubt, impossibility of there being any grounds for doubt.”
For his defense of skepticism, he says, it now remains only to combine the result we have just reached with that at which we arrived in the previous section. Now, I have argued that each of the two propositions deserves, if not our acceptance, at least the suspension of our judgment:
That, in the case of every human being, there is hardly anything, if anything at all, of which he is certain.
That (as a matter of necessity), in the case of every human being, the person knows something to be so only if he is certain of it.”
Of course, these lead us to conclude “that, in the case of every human being, there is hardly anything, if anything at all, which the person knows to be so.”
1. He offers a three-step “defensive” argument; but if it is to be any good, we must be certain of both the “inference" he draws, and of the premises he utilizes! But, he contends, we are unlikely to be certain, and if we are, we will not be able to countenance anything more certain than this inference and these premises! Therefore (?), his "defense" fails?
2. In his “The Pragmatic Dimension of Knowledge,” Fred Dretske develops an analysis of knowledge by critiquing Unger’s argument for skepticism. Dretske maintains that:
...although nothing can be flat if it has any bumps and irregularities, what counts as a bump or irregularity depends on the type of surface being described. Something is empty (another absolute concept according to Unger) if it has nothing in it, but this does not mean that an abandoned warehouse is not really empty because it has light bulbs or molecules in it. Light bulbs and molecules do not count as things when determining the emptiness of warehouses. For purposes of determining the emptiness of a warehouse, molecules (dust, light bulbs, etc.) are irrelevant.
Absolute concepts depict a situation as being completely devoid of a certain sort of thing: bumps in the case of flatness and objects in the case of emptiness. The fact that there can be nothing of this sort present for the concept to be satisfied is what makes it an absolute concept. It is why if X is empty, Y cannot be emptier. Nevertheless, when it comes to determining what counts as a thing of this sort (a bump or an object), and hence what counts against a correct application of the concept, we find the criteria or standards peculiarly spongy and relative. What counts as a thing for assessing the emptiness of my pocket may not count as a thing for assessing the emptiness of a park, a warehouse, or a football stadium. Such concepts, we might say, are relationally absolute: absolute, yes, but only relative to a certain standard. We might put the point this way: to be empty is to be devoid of all relevant things, thereby exhibiting, simultaneously, the absolute in the word `all’) and relative (in the word `relevant’) character of this concept.
...think of knowledge as an evidential state in which all relevant alternatives (to what are known) are eliminated. This makes knowledge an absolute concept but the restriction to relevant alternatives makes it, like empty and flat, applicable to this epistemically bumpy world we live in.
The social or pragmatic dimension to knowledge, if it exists at all, had to do with what counts as a relevant alternative, a possibility that must be evidentially excluded, in order to have knowledge. It does not change the fact that to know one must be in a position to exclude all such possibilities. It does not alter the fact that one must have, in this sense, an optimal justification—one that eliminates every relevant) possibility of being mistaken.
3. A different, and more complicated response to Unger (and to Dretske's argument above) is offered by David Lewis in his "Elusive Knowledge," The Australasian Journal of Philosophy v. 74 (1996), pp. 549-567. It is reprinted in our textbook Knowledge: Readings in Contemporary Epistemology, Sven Bernecker and Fred Dretske, eds. (NY: Oxford UP, 2000) on pp. 366-384 (cf., esp. pp. 371 ff.).
4. See James Cargile’s “In Reply to A Defense of Skepticism.’” I have prepared a supplement for this essay to provide a quick critique of Unger.
 Peter Unger, “A Defense of Skepticism,” Philosophical Review v. 80 (1971), pp. 198-219. These notes are to a reprint of the article in: Knowledge: Readings in Contemporary Epistemology, Sven Bernecker and Fred Dretske, eds. (NY: Oxford U.P., 2000), pp. 324-338.
 Note that there are two spellings: ‘skepticism’ and ‘scepticism’—no difference in position is indicated by the different spellings. The essay is reprinted in Knowledge: Readings in Contemporary Epistemology, Sven Bernecker and Fred Dretske, eds. (N.Y.: Oxford U.P., 2000), pp. 324-338, and these notes are referenced to the reprint edition.
 Philosophers use single quotes (‘‘) to indicate situations where they are speaking about, or mentioning, a word rather than using it. For example in the sentence “The word ‘short’ is not a long word.”, `’short’ is mentioned while ‘long’’ is used. In the sentence about the example sentence (that is, the previous one), both are mentioned!
 Note: ‘p’ stands proxy for any proposition (any assertion or denial). Not all sentences are propositions (questions and commands, for example, don’t make assertions).
 William Alston, “Varieties of Privileged Access, American Philosophical Quarterly v. 8 (1971), pp. 223-241, p. 226. Cf., his brief “Indubitability” in A Companion to Epistemology, eds. Jonathan Dancy and Ernest Sosa (Oxford: Blackwell, 1992), p. 200.
 Fred Dretske, “The Pragmatic Dimension of Knowledge,” Philosophical Studies v. 40 (1981), pp. 363-378, p. 366.
 Ibid., pp. 366-367.
 Ibid., p. 367. Emphasis (bold) added to the passage.
 Ibid., pp. 367-368.
 James Cargile, “In Reply to ‘A Defense of Skepticism,’” Philosophical Review v. 81 (1972), pp. 229-236. It is reprinted in Essays in Knowledge and Justification, eds. George Pappas and Marshall Swain (Ithaca: Cornell U.P., 1972), pp. 337-345, which is on Reserve in Green Library.
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File revised on 09/03/2013.