Sometimes our conversational purposes are not altogether shared, and it is a
matter of conflict whether attention to some far-fetched possibility would
advance them or impede them. What if some farfetched possibility is called to
our attention not by a sceptical philosopher, but by counsel for the defence? We
of the jury may wish to ignore it, and wish it had not been mentioned. If we
ignored it now, we would bend the rules of cooperative conversation; but we may
have good reason to do exactly that. (After all, what matters most to us as
jurors is not whether we can truly be said to know; what really matters is what
we should believe to what degree, and whether or not we should vote to convict.)
We would ignore the far-fetched possibility if we could–but can we? Perhaps at
first our attempted ignoring would be make-believe ignoring, or self-deceptive
ignoring; later, perhaps, it might ripen into genuine ignoring. But in the
meantime, do we know? There may be no definite answer. We are bending the rules,
and our practices of context-dependent attributions of knowledge were made for
contexts with the rules unbent.
If you are still a contented fallibilist, despite my plea to hear the sceptical
argument afresh, you will probably be discontented with the Rule of Attention.
You will begrudge the sceptic even his very temporary victory. You will claim
the right to resist his argument not only in everyday contexts, but even in
those peculiar contexts in which he (or some other epistemologist) busily calls
your attention to farfetched possibilities of error. Further, you will claim the
right to resist without having to bend any rules of cooperative conversation. I
said that the Rule of Attention was a triviality: that which is not ignored at
all is not properly ignored. But the Rule was trivial only because of how I had
already chosen to state the sotto voce proviso. So you, the contented
fallibilist, will think it ought to have been stated differently. Thus, perhaps:
“Psst!–except for those possibilities we could properly have ignored”. And then
you will insist that those far-fetched possibilities of error that we attend to
at the behest of the sceptic are nevertheless possibilities we could properly
have ignored. You will say that no amount of attention can, by itself, turn them
into relevant alternatives.
If you say this, we have reached a standoff. I started with a puzzle: how can it
be, when his conclusion is so silly, that the sceptic’s argument is so
irresistible? My Rule of Attention, and the version of the proviso that made
that Rule trivial, were built to explain how the sceptic manages to sway us–why
his argument seems irresistible, however temporarily. If you continue to find it
eminently resistible in all contexts, you have no need of any such explanation.
We just disagree about the explanandum phenomenon.
I say S knows that P iff P holds in every possibility left uneliminated by S’s
evidence–Psst!–except for those possibilities that we are properly ignoring.
“We” means: the speaker and hearers of a given context; that is, those of us who
are discussing S’s knowledge together. It is our ignorings, not S’s own
ignorings, that matter to what we can truly say about S’s knowledge. When we are
talking about our own knowledge or ignorance, as epistemologists so often do,
this is a distinction without a difference. But what if we are talking about
someone else?
Suppose we are detectives; the crucial question for our solution of the crime is
whether S already knew, when he bought the gun, that he was vulnerable to
blackmail. We conclude that he did. We ignore various far-fetched possibilities,
as hard-headed detectives should. But S does not ignore them. S is by profession
a sceptical epistemologist. He never ignores much of anything. If it is our own
ignorings that matter to the truth of our conclusion, we may well be right that
S already knew. But if it is S’s ignorings that matter, then we are wrong,
because S never knew much of anything. I say we may well be right; so it is our
own ignorings that matter, not S’s.
But suppose instead that we are epistemologists considering what S knows. If we
are well-informed about S (or if we are considering a well-enough specified
hypothetical case), then if S attends to a certain possibility, we attend to S’s
attending to it. But to attend to 5’s attending to it is ipso facto to attend to
it ourselves. In that case, unlike the case of the detectives. the possibilities
we are properly ignoring must be among the possibilities that S himself ignores.
We may ignore fewer possibilities than S does, but not more.
Even if S himself is neither sceptical nor an epistemologist, he may yet be
clever at thinking up farfetched possibilities that are uneliminated by his
evidence. Then again, we well-informed epistemologists who ask what S knows will
have to attend to the possibilities that S thinks up. Even if S’s idle clever
ness does not lead S himself to draw sceptical conclusions, it nevertheless
limits the knowledge that we can truly ascribe to him when attentive to his
state of mind. More simply: his cleverness limits his knowledge. He would have
known more, had he been less imaginative. 17
Do I claim you can know P just by presupposing it?! Do I claim you can know that
a possibility W does not obtain just by ignoring it? Is that not what my
analysis implies, provided that the presupposing and the ignoring are proper?
Well, yes. And yet I do not claim it. Or rather, I do not claim it for any
specified P or W. I have to grant, in general, that knowledge just by
presupposing and ignoring is knowledge; but it is an especially elusive sort of
knowledge, and consequently it is an unclaimable sort of knowledge. You do not
even have to practise epistemology to make it vanish. Simply mentioning any
particular case of this knowledge, aloud or even in silent thought, is a way to
attend to the hitherto ignored possibility. and thereby render it no longer
ignored, and thereby create a context in which it is no longer true to ascribe
the knowledge in question to yourself or others. So. just as we should think,
presuppositions alone are not a basis on which to claim knowledge.
In general, when S knows that P some of the possibilities in which not-P are
eliminated by S’s evidence and others of them are properly ignored. There are
some that can be eliminated, but cannot properly be ignored. For instance, when
I look around the study without seeing Possum the cat, I thereby eliminate
various possibilities in which Possum is in the study; but had those
possibilities not been eliminated, they could not properly have been ignored.
And there are other possibilities that never can be eliminated, but can properly
be ignored. For instance, the possibility that Possum is on the desk but has
been made invisible by a deceiving demon falls normally into this class (though
not when I attend to it in the special context of epistemology).
There is a third class: not-P possibilities that might either be eliminated or
ignored. Take the farfetched possibility that Possum has somehow managed to get
into a closed drawer of the desk-maybe he jumped in when it was open, then I
closed it without noticing him. That possibility could be eliminated by opening
the drawer and making a thorough examination. But if uneliminated, it may
nevertheless be ignored, and in many contexts that ignoring would be proper. If
I look all around the study, but without checking the closed drawers of the
desk, I may truly be said to know that Possum is not in the study–Dr at any
rate, there are many contexts in which that may truly be said. But if I did
check all the closed drawers, then I would know better that Possum is not in the
study. My knowledge would be better in the second case because it would rest
more on the elimination of not-P possibilities, less on the ignoring of
them.18,19
Better knowledge is more stable knowledge: it stands more chance of surviving a
shift of attention in which we begin to attend to some of the possibilities
formerly ignored. If, in our new shifted context, we ask what knowledge we may
truly ascribe to our earlier selves, we may find that only the better knowledge
of our earlier selves still deserves the name. And yet, if our former ignorings
were proper at the time, even the worse knowledge of our earlier selves could
truly have been called knowledge in the former context.
Never–well, hardly ever–does our knowledge rest entirely on elimination and
not at all on ignoring. So hardly ever is it quite as good as we might wish. To
that extent. the lesson of scepticism is right–and right permanently, not just
in the temporary and special context of epistemology.20
What is it all for? Why have a notion of knowledge that works in the way I
described? (Not a compulsory question. Enough to observe that short-cuts–like
satisficing, like having indeterminate degrees of belief–that we resort to
because we are not smart enough to live up to really high, perfectly Bayesian,
standards of rationality. You cannot maintain a record of exactly which
possibilities you have eliminated so far, much as you might like to. It is
easier to keep track of which possibilities you have eliminated if you–Psst!–
ignore many of all the possibilities there are. And besides, it is easier to
list some of the propositions that are true in all the uneliminated, unignored
possibilities than it is to find propositions that are true in all and only the
uneliminated, unignored possibilities.
If you doubt that the word “know” bears any real load in science or in
metaphysics, I partly agree. The serious business of science has to do not with
knowledge per se; but rather, with the elimination of possibilities through the
evidence of perception, memory, etc., and with the changes that one’s belief
system would (or might or should) undergo under the impact of such eliminations.
Ascriptions of knowledge to yourself or others are a very sloppy way of
conveying very incomplete information about the elimination of possibilities. It
is as if you had said:
The possibilities eliminated, whatever else they may also include, at least
include all the not-P possibilities; or anyway, all of those except
for some we are presumably prepared to ignore just at the moment.
The only excuse for giving information about what really matters in such a
sloppy way is that at least it is easy and quick! But it is easy and quick;
whereas giving full and precise information about which possibilities have been
eliminated seems to be extremely difficult, as witness the futile search for a
“pure observation language.” If I am right about how ascriptions of knowledge
work, they are a handy but humble approximation. They may yet be indispensable
in practice, in the same way that other handy and humble approximations are.
If we analyse knowledge as a modality, as we have done, we cannot escape the
conclusion that knowledge is closed under (strict) implication.21 Dretske has
denied that knowledge is closed under implication; further, he has diagnosed
closure as the fallacy that drives arguments for scepticism. As follows: the
proposition that I have hands implies that I am not a handless being, and a
fortiori that I am not a handless being deceived by a demon into thinking that I
have hands. So, by the closure principle, the proposition that I know I have
hands implies that I know that I am not handless and deceived. But I don’t know
that I am not handless and deceived–for how can I eliminate that possibility?
So, by modus tollens, I don’t know that I have hands. Dretske’s advice is to
resist scepticism by denying closure. He says that although having hands does
imply not being handless and deceived, yet knowing that I have hands does not
imply knowing that I am not handless and deceived. I do know the former, I do
not know the latter.22
What Dretske says is close to right, but not quite. Knowledge is closed under
implication. Knowing that I have hands does imply knowing that I am not handless
and deceived. Implication preserves truth-- that is, it preserves truth in any
given, fixed context. But if we switch contexts midway, all bets are off. I say
(1) pigs fly; (2) what I just said had fewer than three syllables (true); (3)
what I just said had fewer than four syllables (false). So “less than three”
does not imply “less than four”? No! The context switched midway, the semantic
value of the context-dependent phrase “what I just said” switched with it.
Likewise in the sceptical argument the context switched midway, and the semantic
value of the context-dependent word “know” switched with it. The premise “I know
that I have hands” was true in its everyday context, where the possibility of
deceiving demons was properly ignored. The mention of that very possibility
switched the context midway. The conclusion “I know that I am not handless and
deceived” was false in its context, because that was a context in which the
possibility of deceiving demons was being mentioned, hence was not being
ignored, hence was not being properly ignored. Dretske gets the phenomenon
right, and I think he gets the diagnosis of scepticism right; it is just that he
misclassifies what he sees. He thinks it is a phenomenon of logic, when really
it is a phenomenon of pragmatics. Closure, rightly understood, survives the
test. If we evaluate the conclusion for truth not with respect to the context in
which it was uttered, but instead with respect to the different context in which
the premise was uttered, then truth is preserved. And if, per impossibile, the
conclusion could have been said in the same unchanged context as the premise,
truth would have been preserved.
A problem due to Saul Kripke turns upon the closure of knowledge under
implication. P implies that any evidence against P is misleading. So, by
closure, whenever you know that P. you know that any evidence against P is
misleading. And if you know that evidence is misleading, you should pay it no
heed. Whenever we know–and we know a lot, remember–we should not heed any
evidence tending to suggest that we are wrong, But that is absurd. Shall we
dodge the conclusion by denying closure? I think not. Again, I diagnose a change
of context. At first, it was stipulated that S knew, whence it followed that S
was properly ignoring all possibilities of error. But as the story continues, it
turns out that there is evidence on offer that points to some particular
possibility of error. Then, by the Rule of Attention, that possibility is no
longer properly ignored, either by S himself or by we who are telling the story
of S. The advent of that evidence destroys S’s knowledge, and thereby destroys
S’s licence to ignore the evidence lest he be misled.
There is another reason, different from Dretske’s. why we might doubt closure.
Suppose two or more premises jointly imply a conclusion. Might not someone who
is compartmentalized in his thinking–as we all are–know each of the premises
but fail to bring them together in a single compartment? Then might he not fail
to know the conclusion? Yes; and I would not like to plead idealization-ofrationality
as an excuse for ignoring such cases. But I suggest that we might
take not the whole compartmentalized thinker, but rather each of his several
overlapping compartments, as our “subjects.” That would be the obvious remedy if
his compartmentalization amounted to a case of multiple personality disorder;
but maybe it is right for milder cases as well.23