Grice directs his attention to a number of issues raised by Moore's famous “A Defense of Common Sense.”  Grice recapitulates a list of things which Moore claims to know with certainty with regard to himself, together with a further list of corresponding things which Moore claims to know that very many other people know with regard to themselves.  Grice notes various claims which Moore makes with respect to the propositions which figure in this alleged body of knowledge:     — that the acceptance of their truth does not have to await a determination of the meaning of the expressions which are used to report them;     — that the kind of knowledge he is claiming requires no mysterious faculties, but rests on the possibility of knowing things the evidence for which one no longer remembers; and     — that while Moore is defending Common Sense against the philosophers his claim is only (the "Common Sense" view of the world is in certain fundamental features wholly true, it is not claimed that no Common Sense beliefs are vulnerable to philosophical attack.     Grice suggests that, in Moore's view, the prime sin committed by those who improperly question Common Sense would be that of questioning or denying things which they both in fact and, according to Moore, know with certainty to be true, a sin the authenticity of which depends crucially on Moore's claims to knowledge with certainty.     Grice distinguishes two different varieties of skepticism concerning empirical propositions about material things or about other minds, which for brevity I referred to merely as "empirical propositions."     The first, which Grice is inclined to regard — he later suspected wrongly — as the less interesting and important variety of skepticism, holds that not merely is no empirical proposition ever known with certainty to be true, but no such proposition is ever known to be more probably true than false.     I connected this version of skepticism with two different interpretations of Descartes's discussion in the First Meditation of the  "Malignant Demon";     And Grice suggests — he now think overoptimistically — that, on either interpretation, Descartes's argument fails to establish this kind of skepticism even as an initial stumbling block clamoring to be removed by further metaphysical reflection.     The second (and Grice thought then), the more interesting, variety of skepticism denies merely that any empirical proposition is ever known with certainty to be true but allows that the truth of such propositions may be a matter of the highest possible degree of probability.     To this form of skepticism Grice considers a number of objections, some of them fairly well known.     To some of these objections Grice sketches a reply which Grice thinks might leave the skeptics' position intact.     Grice’s primary interest, however, is declared to lie in a final objection, to Grice’s mind the most serious and radical objection.    This objection is most clearly propounded by Malcolm  In The Philosophy of G. E. Moore, ed. Schilpp; cf. also "Certainty and Empirical Statements," Mind    The Skeptic, when he claims that neither he nor anyone else *knows*, for example, that there is cheese on the table, is in a very odd position.     He is not suggesting that what appears to be cheese might just possibly turn out to be soap, nor that we have not looked to see whether the appearance might not be the effect of a conjuring trick performed with mirrors, nor even that though we have been quite careful to eliminate the possibility of error, we have not been quite careful enough, and if we went on a bit (or a lot) longer with our tests we should be better off and should be able finally to say  "Now I know."     The Skeptic will still refuse to admit that we can say correctly "I know" however long we continue with our test (and this goes not only for there is cheese on the table but for every other empirical proposition as well).     Since, therefore, the accumulation of further evidence is irrelevant to the dispute between the Skeptic and his opponent, the Skeptic's thesis must be an A PRIORI one, namely that to say that, for example     "I know that there is cheese on the table"     is to assert (or try to assert) something self-contradictory or logically absurd.    But this contention on the part of the Skeptic, says Malcolm, itself involves a self-contradiction or logical absurdity when taken in conjunction with something else which the Skeptic will have to admit.    For the Skeptic will have to admit that     I know there is cheese on the table    is an ordinary expression, where by "ordinary expression" Malcolm means     an expression that has an ordinary use, i.e. an expression that is ordinarily used to describe a certain sort of situa-tion"     an "ordinary expression" need not in fact ever be used—    There is a mermaid on the table.    is an ordinary expression — but it must be such that it would be used to describe a certain sort of situation if that situation existed or were believed to exist.    The Skeptic then will have to admit that     "I know that there is cheese on the table"     is in this sense an ordinary expression, and so, to remain a Skeptic, he will have to maintain that     some ordinary expressions are self-con-tradictory or absurd.     But this is itself an absurdity, since a self-contra-dictory expression is by definition one which would never be used to describe any situation whatever.     If that is so, it is absurd to suggest that any expression is both self-contradictory and an ordinary expres-sion.     But this is just what the Skeptic is maintaining as regards "    I know that there is cheese on the table."     Some philosophers, paying a charitable tribute to the perspicacity of their Skeptical colleagues, have suggested that in view of the argument just stated, the latter cannot have been intending to deny the correctness of the "ordinary" use of the word "know," but must (very misleadingly) have been either (a)   insisting on using the word "know" in a way of their own, or (b)     suggesting a change in the existing usage.    Grice not think Skeptics would be very happy about either of these interpretations of their intentions.    Grice now turns his attention to an attempt to construct a line of defense for the Skeptic against this very serious objection.     Grice may at this point say, in order to forestall the possibility of snorts of disapproval from hus audience that Grice is not myself a Skeptic;     but Grice does think that the Skeptical position is liable to be somewhat cavalierly treated as hopeless.    The Skeptic might admit that, in his view, it is always an incorrect use of language to say     "I know that there is cheese on the table,"     and he might also admit that it was the kind of incorrect use of language which is self-contradictory — plainly not all incorrect use of language involves a self-contradiction.    He might also admit that in some sense of "ordinary use" no self-contradictory expression has an ordinary use and that in some sense of ordinary use such expressions as "    I know that there is cheese on the table"     do have an ordinary use.     But he might go on to pose the question whether the senses of "ordinary  just mentioned are the same sense.    Consider what Grice takes to be Malcolm's definition of a self-contradic-tory expression, namely "    an expression which would never be used to describe any situation"     Malcolm does not actually say that this is a complete definition of "self-contradictory expression," but equally he does not say that it is not, and Grice strongly suspects that Malcolm intends it as such, as indeed his manner of expression suggests).     Is it really satisfactory as it stands?     Take the expression     "I'm not copperbottoming’em, ma'am, I'm aluminiuming 'em, ma'am."     I doubt very much if this expression would ever be used to describe any situation;     It is too difficult to enunciate, and certainly no one would think of using it as a written symbol with a descriptive use     Grice of course is not using it descriptively.     It would no doubt be possible to fill in the gaps in    "The  —archbishop fell down the-  —stairs and bumped-  like—"     with such a combination of indecencies and blasphemies that no one would ever use such an expression.     But in neither of these cases would we be tempted to describe the expressions as self-contradictory.     Indeed, the number of possible reasons why an expression would in fact never be used might be, as far as Grice can see, in principle unlimited.     Should we not then have to amend Malcolm's definition by adding a specification of the particular reason which would preclude the use of a self-contradictory expression?     But if we did that should we not have to say "because to use it would be to say something self-contradictory"?     But we are now defining "self-contradictory" in terms of itself.    But is it *even* true that a self-contradictory expression is never in fact used to describe any situation?     No doubt if they are used to describe a situation, they do not succeed in describing that situation, but that is another matter.     Might I not, as a result of miscalculation, say "    there are eight lots here, each containing eight eggs; so there are sixty-two eggs."     Malcolm perhaps would say that Grice would be, in this case, employing the expression "sixty-two" to mean what is normally mean by "sixty-four";     but such a suggestion would surely be most counterintuitive.    And a well-constructed "catch-question," such as a VOCAL utterance of the words     "can you write down 'there are two ways of spelling—?"     where the actual utterer substitutes for     —     — a sound represented by "throo," —     may elicit from a large number of persons the *absurd* answer "Yes."    If, then, the Skeptic is admitting that expressions such as     "I know that there is cheese on the table"     have in a sense an ordinary use (in that they are sometimes used descriptively), he might claim to be admitting nothing inconsistent with their being self-contradictory (i.e. having no ordinary use in some other sense of "ordinary use").     But he would have to admit not merely that such expressions are sometimes used to describe certain kinds of situations but that they are very frequently indeed used to describe such situations.     The question remains then     "Is it logically possible for it to be true that most people would usually, or more often than not, use an expression 'p' to describe a certain kind of situation, and yet be false that 'p' is a correct description of that situation (or perhaps of any situation, in which case it would be self-contradictory)?"     The Skeptic would have to maintain that it is.     An imaginary illustration may illuminate the path we might take.    Suppose a state of society in which our linguistic behaviour were such that all of us, on most occasions when we wished to describe a situation involving a rose, used expressions such as "    that is a cauliflower" (    or other suitable expressions containing the word "cau-liflower");     and all of us on all occasions also used expressions containing the word "cauliflower" to describe cauliflower situations.    Suppose, however, also that, on all those occasions when we had before our minds the thought both of a rose and a cauliflower (for ex-ample, when our attention was drawn to our practice of using the word "cauliflower" in descriptions both of rose situations and cauliflower situations),     we then called a rose "a rose" and refused to call it "a cauliflower" and insisted that on all the occasions when we had called "a rose" "a cauliflower" we had been wrong.     In such a state of society would the  "cauliflower" be a correct expression to use to refer to a rose?     Should we say, confronted with such linguistic be-havior,      that "cauliflower" would be a correct expression to use to refer to a rose (that is, that "cauliflower" would be ambiguous and would in one sense apply to roses and in another apply to cauliflow-ers; or      that the question is undecidable, that we would not know whether to say that it would be correct or to say that it would be incorrect to apply the expression "cauliflower" to roses (that is, that the situation would fall within the margin of vagueness between"being correct" and "being incorrect"); or (3)     that we are uncertain about this question, but are somewhat inclined to alternative (2)?    Now the Skeptic, I think, may be maintaining that something like this is the case with regard to the common use of the word "know."     We all frequently do apply the word "know" to empirical propositions (just as in the imaginary example we in fact call roses "cauli-flowers");     but the Skeptic would claim that for every situation to describe which we are inclined to use the expression "I know p" (where p is an empirical proposition) he could produce some proposition     q (in his notorious arguments for example, q might be I may be dream-ing)     such that (1) we should admit that     q is logically incompatible with I know p, and (2) we should deny I know p rather than deny q.    In other words he could produce arguments to show that if we reflected adequately, we should always correct our application of the word "know" to empirical propositions.    Assume for the moment that the Skeptic is right in his ability to produce arguments to show that we should so correct our use of the word "know."     How in that case do we stand? (1)     If answer (1) to the  "cauliflower" problem is right (namely that "cauliflower" would be a correct expression to use to refer to a rose), presumably, however good the Skeptic's arguments to show that on reflection we should abandon our application of the word "know" to empirical propositions, the Skeptic will be entirely wrong and his opponent entirely right.     If answer (2) to the "cauliflower" problem is right (namely the question is undecidable), presumably the Skeptic will be right insofar as he denies his opponent's thesis that it is definitely correct to apply the word "know" to empirical propositions, and will be wrong insofar as he himself asserts that it is definitely incorrect to do so.     If answer (3) to the "cauliflower" problem is right (namely that "cauliflower" would not be a correct expression to apply to roses), presumably the Skeptic would be entirely right and his opponent entirely wrong.    Grice concludes by just listing some possible arguments which the Skeptic might use in defense of this thesis (which Grice has put into his mouth) that we should on reflection abandon our use of expressions such as "    I know p"     (where p is an empirical proposition).     Grice is doubtful if any of them will work (and we should of course remember that the traditional Skeptical arguments turning on the use of the phrase  "it is always possible that" have already been exploded).    But Grice does not have time to consider them in detail.    The Skeptic might argue as follows:     If it is to be true that I know an empirical proposition p to be true, it must also be true that I have conclusive evidence for p.     But we cannot say without self-contradiction     "I had conclusive evidence for p but p was false,"     whereas if p is an empirical proposition, we can always say without selfcontradic-tion     the evidential propositions which support p are true, but p is false."     Since therefore (the Skeptic might say) we shall have to admit that the evidence for an empirical proposition is never conclusive, we shall have to correct our use of the word "know."    He might argue:     If it is proper for me to say '    I know that there is cheese on the table,     I shall have to claim (if I am asked) to know that future observations on the part of myself and of others will not render the proposition there is cheese on the table doubtful."     But we are reluctant under pressure to make such claims to knowledge of propositions about the future.    He might note that it seems very odd to say "    I know p but I might have had better evidence for p than I do in fact have,    " but if p is an empirical proposition (the Skeptic would say), I shall have to admit this odd statement as being true.    For it to be true (the Skeptic might say) that     I know that s is p (where s is p is an empirical proposition),     The a is b    Subject is Preficate    it would have to be true that I know that no one has ever had as good evidence for some other proposition, say s, is p as I have for s is p, and yet have been wrong in asserting that s is p.     If I cannot claim this, someone may say     "What is the difference between your evidence for “S is P” and some other person's evidence for     “S is P”    which entitles you to claim that     you know that     s is p     and yet admit that he may not have known that s, is p?"     I think this would be a difficult question to answer (or rather avoid answering).    Now take the proposition     I have a body.    — (not obviously amenable to Skeptical treatment.    Do I know that no disembodied spirit has ever had as good evidence for the proposition that it (or he) has a body as I now have for the proposition that I have a body?     To know this, either I must claim to know that there are no disembodied spirits, or I must claim that even if there are disembodied spirits, none of them has ever been systematically deceived in such a way as to have all the sensations (etc.) which provide evidence for the existence of one's own body, though he (it) in fact has no body.     Am I prepared to say that I *know* one or the other of these things?"         H. P. Grice.