ISSN 1393-614X Minerva - An Internet Journal of
Philosophy Vol. 8 2004.
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TRACKING,
RELIABILISM, AND POSSIBLE WORLDS
Wesley Cooper
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Abstract
Robert Nozick’s tracking account of knowledge is
defended against Colin McGinn’s criticisms by drawing on David Deutsch’s
’multiverse’ conception of possible worlds. Knowledge on the tracking account
requires a ’method’ or ’way’ of believing. Exploiting this feature undercuts
the apparent force of McGinn’s counter-examples.
This essay focuses on Colin McGinn’s critique in Knowledge and
Reality of Robert Nozick’s tracking account of knowledge in Philosophical
Explanations. Nozick offers a crisp portable statement of the tracking theory
as follows, where S is some knowing subject and p is some proposition
known.
1. p is true.
2. S believes that p.
3. not-p → not-(S believes that p.
(the variation condition)
4. p → S believes that p.
(the adherence condition)
The
arrow relates antecedent to consequent in the manner of the subjunctive
conditional: if the antecedent weren’t true, then the consequent wouldn’t be
true. If Hermia knows that Lysander is waiting for her in the woods, then if
Lysander weren’t waiting for her in the woods, she would not believe so
(variation); and if Lysander were waiting for her in the woods, Hermia would
believe that (adherence).
It
is important that a more technical and complete statement – about S knowing via
method (or way of believing) M that p – lies in the background.
1. p is true.
2. S believes, via method or way of coming to believe M, that
p.
3. If p weren’t true and S were to use M to arrive at
a belief whether (or not) p, then S wouldn’t believe, via M, that p.
4. If p were true and S were to use M to arrive at a
belief whether (or not p, then S would believe, via M, that p.
The
more complete statement is important for putting McGinn’s counter-examples to
the tracking theory into perspective, and for evaluating his diagnosis that it
suffers from being a “local” version of reliabilism as opposed to his own
“global” version.
This
diagnosis is replaced here by the interpretive frame that McGinn and Nozick
offer versions of reliabilism differing about whether capacities or
subjunctives should be fundamental, and that when this issue is sorted the two
versions play complementary roles in a fuller reliabilist theory, in which
neither capacities nor subjunctives is fundamental. McGinn makes a good case
that discriminative capacities are significant for the theory of knowledge, but
a certain realism about possible worlds shows how the tracking theory might be
more basic: capacities imply subjunctive conditionals, and possible worlds
might be the truth-makers for these. The many-worlds or multiverse hypothesis
is suggested as an appropriate form of realism about possible worlds, anchoring
the relevant counterfactuals in the multiverse, representing all physically
possible worlds, while bypassing issues about modal realism pertaining to
worlds that are alleged to be knowable a priori. The multiverse is
knowable a posteriori as implied by a scientific hypothesis, not apriori
as implied by the truth conditions of modal sentences. McGinn is plausibly
critical of modal realism of the latter sort, with special reference to David
Lewis; but the multiverse version of modal realism is motivated by wholly
different considerations than Lewis’s, empirical arguments from physics that
are untouched by McGinn’s criticisms.
Talk
about capacities, abilities, powers, dispositions and the like is vague at
best. Even when identified with their “categorical bases” in micro-structure,
that structure guarantees the capacity only if it supports appropriate
subjunctive conditionals. (Opium’s “dormitive power” may be such-and-such
micro-structure, but only if that structure would put one to sleep if
ingested.) Those conditionals in turn backstop the structure by referring to
what it actually does in other physically possible worlds. (There is a world in
the multiverse where this opium puts one to sleep, though in this world it
remains in the medicine cabinet.) The upshot is that McGinn’s and Nozick’s
versions of reliabilism are in effect the same analysis at different levels –
less and more fundamental ones, respectively.
McGinn’s first
counter-example to tracking asks the reader to
[s]uppose we are living in a universe in which there
also exists a benevolent deity who watches over our sensory input: he has the
intention to preserve this input by artificial means in the event of a
cataclysm in which the material objects that actually produce it should
suddenly go out of existence. Let us suppose that this cataclysm is, in fact,
physically possible and that the deity has the power to carry out his
intention. Then it seems that we have the truth of this counterfactual: ’If the
objects around me were to go out of existence, I would still believe that I was
surrounded by those objects’ – since the deity would see to it that my
experience sustained this belief were the cataclysm to occur. (We also, of
course, have the adherence condition satisfied in this case.) Yet I am
reluctant to say that, because of these facts, we do not know that we
are surrounded by material objects: for the truth of the counterfactual does
not, intuitively, make our true belief that we are surrounded by material
objects merely accidentally true. Suppose that in the whole history of
the universe the cataclysm never in fact occurs, though if it had the
deity would have intervened to preserve our beliefs: can we really say that we
do not then know, for example, that the earth exists? (McGinn 1999, pp.
8-9)
But
consider two ways of knowing that the denizens of this universe might employ,
an immanent method that relies exclusively on sense experience, and an
immanent-plus or transcendental method that is proof against deception by
transcendent entities. Disclaiming a transcendental method allows the denizens
to know. The immanent method might be restated as requiring, as McGinn writes,
“some condition that speaks of the person’s propensity to believe the truth
with respect to a range of distinct ’relevant’ propositions.” Insistence on
this requirement is the distinctive feature of his global reliability theory.
Since this is to be incorporated into the tracking account, it is fair to
specify the method in this way. There is no reason to polarize McGinn’s
reliabilism as global and Nozick’s as local, because Nozick’s analysis includes
reference to method as well as the four conditions in the portable version, and
method can be specified, as it just was, so as to avoid counter-examples.
McGinn attends to the portable statement of the tracking theory, dismissing the
references to method in the fuller statement as “some minor refinements.” This
neglect is responsible for the polarizing.
In
passing, note that McGinn’s assumption about the physical possibility of the benevolent-deity-universe
is not innocent, at least when the tracking theory is integrated with the
multiverse hypothesis. True counterfactuals are grounded in actual events in
the multiverse, so the ones that figure in the counter-example are false, as surely
as the physics-defying antics in Road Runner cartoons.
Having
defended the necessity of the variation condition, turn now to McGinn’s
counterexample to its sufficiency.
You visit a hitherto unexplored country in which the
inhabitants have the custom of simulating being in pain. You do not know that
their pain behaviour is mere pretense, and so you form the belief of each
person you meet that he or she is in pain; imagine you have acquired a great
many false beliefs in this way. There is, however, one person in this country
who is an exception to the custom of pain pretence: this hapless individual is
in constant pain and shows it (we can suppose that he falsely believes others
to be in his unfortunate condition – he has not been told of the pretence by
the others). You also believe of this person, call him N, that he is in
pain. Now I take it that we would not say that your true belief that N
is in pain counts as knowledge, for it is, intuitively, a mere accident that
your belief is true in this instance. But now consider the relevant
counterfactuals, in particular ’if N were not in pain, you would not
believe that N was in pain’: this counterfactual is true in the
envisaged circumstances, since if N were not in pain then (unlike the
pretenders around him) he would not behave as if he was, and so you would not
believe that he was. So your belief that N is in pain does track
the truth of that proposition even though it does not rank as knowledge.
(McGinn 1999, pp, 11-12)
But
consider two methods or ways of knowing that you might be using. One relies on
induction from the pretenders to the hapless individual. The other is a one-off
method: it sizes up the individual as a pain-sufferer without the benefit of
inference from observation of the pretenders. If you were using the one-off
method, your belief about the individual would be knowledge. But the
counter-example stipulates in effect that you are using the other method, and
consequently your belief is tainted – not by the insufficiency of the variation
condition, but by the method you used, which doesn’t mesh well with this
hitherto unexplored country. The method includes a folk-psychological theory,
in particular about when pain behavior can be expected, that happens to be
wildly misleading in this country.
These
replies to the counterexamples suggest that the differences between McGinn’s
and Nozick’s versions of reliabilism are merely notational. The references to a
broad range of propositions in McGinn are brought into Nozick by a “method or
way of knowing.” Moreover, McGinn requires local reference to a specific known
proposition, like the one that figures in the variation and adherence
conditions, in order to cope with counterexamples similar to the ones he poses.
So local-versus-global doesn’t frame helpfully the relationship between the two
versions of reliabilism.
Suppose
again that we are living in the universe of the benevolent deity. This time
however a cataclysm actually occurs at noon on a certain day, and the deity
implements his policy of intervening to paper it over, producing in us
convincing but illusory experience as of material objects. Before noon and
after noon there really are material objects, and correspondingly we have
knowledge of a range of propositions about them. But at noon we lack such
knowledge, and the corresponding proposition about our knowledge of them is
false. So McGinn’s analysis of S knows that p must include not only
reference to a range of propositions about which S can discriminate truth from falsehood,
such as those about the world before and after noon, but also explicit
provision that p belongs in that range (or not, as in the preceding
revision of McGinn’s thought-experiment). Like Nozick’s analysis, it must have
local features as well as global ones. This can be brought out as well in the
thought-experiment about the unexplored territory, where the traveller might
figure out the widespread pretence and notice something about the genuine pain
sufferer that sets him apart. His knowledge of this person’s pain is not
tainted by the widespread pretence, as it is in the first version of the
experiment. McGinn’s analysis of S knows that N is in pain must do the
local work of determining whether S is tracking N’s being in pain, in addition
to the global work of specifying whether S’s method of knowing is tainted by
widespread pretence.
McGinn
would not want to rephrase his analysis in these terms, preferring brute appeal
to discriminative capacities over the tracking theory’s appeal to subjunctives.
He writes:
The point is that it is unsatisfactory to employ
counterfactuals in a primitive way in one’s analysis of categorical
propositions; they have dependent truth value. We can always
legitimately ask what makes a given counterfactual true and expect to be
presented with a suitable categorical fact. Now it seems to be that this
general thesis imposes a constraint upon philosophical analyses, to the effect
that we should be able to say what categorical propositions ground the
counterfactuals we employ in the analysis....if non-circular categorical
grounds can be produced it seems that the counterfactuals are in
principle dispensable in the analysis; they serve merely as an eliminable
intermediate or interim step to the real analysis, which is categorical in
form....[W]e are entitled to press Nozick on the question what makes his
tracking counterfactuals true: what categorical facts about the believer
S and S’s relation to the world make it true that if it weren’t the case
that p S would not believe that p and if it were S would?
(McGinn 1999, p. 16)
He
believes that a satisfactory analysis would reveal the categorical facts upon
which subjunctive conditionals depend. This is not unreasonable, but on the
other hand his own preference for capacities is questionable for the reasons
given earlier, about vagueness and inseparability from subjunctives. Is there a
deeper level of analysis?
Both
Nozick and McGinn are willing to rephrase the tracking theory in terms of
possible worlds. Nozick writes,
This point [about the power and intuitiveness of the
subjunctive condition] is brought out especially clearly in recent
’possible-worlds’ accounts of subjunctives: the subjunctive is true when
(roughly) in all those worlds in which p holda true that are closest to
the actual world, q also is true. (Examine those worlds in which p
holds true closest to the actual world, and see if q holds true in all
these.) Whether or not q is true in p worlds that are still
farther away from the actual world is irrelevant to the truth of the
subjunctive. (Nozick 81, p. 174)
And in the
same vein McGinn writes,
Putting these two conditions [variation and adherence]
in terms of the usual possible worlds semantics for counterfactuals, we can say
that S has knowledge that p iff (i) in all possible worlds closest to
the actual world in which p does not hold S does not believe that p,
and (ii) in all those close worlds in which p does hold S believes that p:
belief that p is not preserved in the close not-p worlds and it
is preserved in the close p worlds. (McGinn 1999, p. 9)
A
possible-worlds account of subjunctives/counterfactuals is formal, in that it
does not entail or exclude the various conceivable interpretations that give it
content. Not excluded in particular is an interpretation that construes its
possible worlds as the physically possible worlds of the multiverse. Lewisian
modal realism is another interpretation, one that isn’t restricted to
physically possible worlds and, at least in Lewis’s favoured account, does not
allow interaction between worlds (though he explores the logic of overlapping
worlds). That multiverse worlds aren’t the same as Lewis’s doesn’t prevent the
former from belonging to a legitimate interpretation of possible-worlds
semantics. Nozick and McGinn regard this semantics as nothing more than a
paraphrasing or formalizing device, but their agreement on this point does not
settle the matter about whether the multiverse hypothesis can interpret its
worlds more deeply, as grounding subjunctives. Nozick disclaims anything more
(p. 81), and McGinn argues at length against Lewisian modal realism, which
attempts to extract ontological consequences from the truth conditions of modal
sentences. Although he surmises that “Lewis’s metaphysics is the only way to
make clear and honest sense of an ontology of possible worlds,” the horizon of
this claim is limited to theorists like Lewis, Robert Stalnaker, and Saul
Kripke who derive the ontology a priori. There is a clear path therefore
for a narrow, a posteriori derivation of a possible-worlds ontology that
grounds subjunctives. Nozick’s disclaimers, Lewis’s defense of modal realism,
and McGinn’s skepticism about it leave that path open. (I am indebted in
this paragraph to Jim Stenberg.)
David
Deutsch’s account in The Fabric of Reality serves as an accessible
statement of the multiverse interpretation of these experiments. (See
also Deutsch 1985.) They have to do with interference phenomena, which on the
multiverse account are the effects of a particle in one universe on its
counterpart in another. So when a photon is shot through a slit toward a
barrier in an interference experiment, the resulting pattern on the barrier is as
if the photon had collided with an invisible “shadow” photon coming through
one of the other slits. The multiverse hypothesis takes this appearance at face
value. Other options include the hypothesis that the photon exhibits
wave-particle duality (Bohm’s interpretation), and the hypothesis that science
should refrain from metaphysical speculation about what’s really going on in
such experiments (the Copenhagen interpretation). Deutsch makes a case for
scientific realism over instrumentalism and consequently rejects the Copenhagen
interpretation and its like. He suggests that the issue between Bohm’s
allegedly single-universe interpretation of quantum theory and the many-worlds
view is ultimately to be decided by appeal to complexity theory.
Deutsch
assumes that degree of complexity will be a function of amount of computation,
reasoning that
[w]orking out what Bohm’s invisible wave will do
requires the same computations as working out what trillions of shadow photons
will do. Some parts of the wave describe us, the observers, detecting and
reacting to the photons; other parts of the wave describe other versions of us,
reacting to photons in different positions. Bohm’s modest nomenclature –
referring to most of reality as a ’wave’ – does not change the fact that in his
theory reality consists of large sets of complex entities, each of which can
perceive other entities in its own set, but can only indirectly perceive
entities in other sets. These sets of entities are, in other words, parallel
universes. (Deutsch 1997, p. 56)
So
Bohm’s variables are in effect under-interpreted and not fully explanatory.
Just as Ptolemaic epicycles, if fully interpreted/explanatory, would give a
Galilean description of the movement of planets, so too Bohmian variables would
yield a multiverse. The epicycles are really tracking Galilean motion,
and the variables are really tracking multiverse phenomena. (For a
philosopher’s defense of Bohm see Christopher Norris’s Quantum Theory and
The Flight from Realism. See that work and also his “Should philosophers
take lessons from Quantum Theory” for criticism of Deutsch. For a scientific
journalist’s sympathetic discussion of Deutsch, see Julian Brown’s The Quest
for the Quantum Computer.)
Deutsch
holds that classical spacetime physics, understood deterministically as it is
on his view, implies that counterfactuals have no meaning. All that can happen
does happen. This doesn’t trouble him, however, because the multiverse is
bigger than spacetime. (“To a first approximation, the multiverse is like a
very large number of co-existing and slightly interacting spacetimes.” (Deutsch
97, p. 275) So reality includes universes in which objective facts make our
counterfactuals true.
A
historian might make the judgment that ’if Faraday had died in 1830, then
technology would have been delayed for twenty years’....There is nothing arbitrary
about which variants of our universe the counter-factual ’if Faraday had died
in 1830...’ refers to: it refers to the variants which really occur
somewhere in the multiverse. That is what resolves the ambiguity. Appealing to
imaginary universes does not work, because we can imagine any universes we
like, in any proportions we like. But in the multiverse, universes are present
in definite proportions, so it is meaningful to say that certain types of event
are ’very rare’ or ’very common’ in the multiverse, and that some events follow
others ’in most cases’....Therefore the ’if...then...’ statement can
unambiguously be taken to mean ’in most universes in which Faraday died in
1830, technological progress was delayed relative to our own.’ (Deutsch 97, p.
276)
The analysis being floated, integrating the multiverse with Nozick’s
and McGinn’s accounts of knowledge, is not an argument for the truth of the
multiverse hypothesis or a declaration of its truth. Rather, the possibility
that it is true recommends a satisfying integration of McGinn’s and Nozick’s
versions of reliabilism and what may be our best science about the cosmos. That
the proposal is not idle speculation is indicated by its standing among string
theorists and quantum cosmologists. For instance, Michael Clive
Price's The Everett FAQ reports that "political
scientist" L David Raub polled 72 of the "leading cosmologists and
other quantum field theorists" about the "Many-Worlds
Interpretation." Raub gave the following response breakdown.
1. "Yes, I think MWI is true"
58%
2. "No, I don’t accept MWI"
18%
3. "Maybe it’s true but I’m not
yet convinced" 13%
4. "I have no opinion one way or
the other" 11%
Price writes
Amongst the "Yes, I think MWI is true" crowd
listed are Stephen Hawking and Nobel Laureates Murray Gell-Mann and Richard
Feynman. Gell-Mann and Hawking recorded reservations with the name
"many-worlds", but not with the theory’s content. Nobel Laureate
Steven Weinberg is also mentioned as a many-worlder, although the suggestion is
not when the poll was conducted, presumably before 1988 (when Feynman died).
The only "No, I don’t accept MWI" named is Penrose.
The findings of this poll are in accord with other
polls, that many-worlds is most popular amongst scientists who may rather
loosely be described as string theorists or quantum gravitists/cosmologists. It
is less popular amongst the wider scientific community who mostly remain in
ignorance of it.
This
is enough perhaps to recommend a tracking analysis, at least in the spirit of
Nozick’s conception of philosophical explanation as opposed to coercive proof.
Starting
from the possible-worlds construal that Nozick and McGinn both accept, these
worlds are interpreted as the physically possible, parallel worlds of the
multiverse. Subjunctives now have categorical bases, as McGinn requests; they
are grounded in an actual world, one that exists just as ours does, in which
the antecedent is true. The subjunctive form of the tracking theory is
vindicated as an interim analysis. And its subjunctives help define the
discriminative capacities that figure in McGinn’s version, which may now be
called the third tier of the tracking theory of knowledge.
This
tier’s serious work is what McGinn envisages for it. Its key notion of
discriminative capacity could unify propositional knowledge with knowing how,
knowing who, and other forms of knowledge. Propositional knowledge emerges as
fundamental (contrary to McGinn’s expectation on this point) because of its
role in the basic, “categorical” possible-worlds tier and in the second-level
or “interim” tier given by Nozick’s subjunctive statement of the tracking
theory.
Not
every objection levelled by McGinn against Nozick has been taken up here. In
particular, Nozick’s treatment of mathematical knowledge has not been defended.
(It drops the variation condition because hypothesizing the falsehood of
mathematical propositions, as in “If it were not the case that 2 + 2 = 4....”,
may fail to make sense.) On the other hand, if McGinn’s discriminatory-capacity
version of reliabilism is correctly framed as the third tier of the tracking
theory, its capacities may be called upon to explain how mathematical knowledge
works, not by way of confounding the tracking theory but by contributing to an
improved version of it.
The
most troubling question that has been more begged than answered here is about
the relationship between subjunctives or counterfactuals, on one hand, and
capacities, capabilities, abilities, powers, and so on, on the other hand. The
three-tier version of the tracking theory implies that subjunctives are
logically prior to capacities, whereas McGinn urges the opposite, as in the
following passage.
In the first place, it seems to me that this
explication [of capacities by reference to counterfactuals gets the logical
priority the wrong way around; for I would hold, quite generally, that an
ascription of capacity is what grounds the associated counterfactuals–it is not
that the capacity ascription is true in virtue of the truth of the
counterfactuals. This claim is, I think, just a corollary of the general
position about counterfactuals and categoricals that I allied myself with
earlier: the counterfactuals about what someone would do in such-and-such circumstances
are true because (inter alia) the person has a certain capacity–the
person does not have the capacity because he satisfies the associated
counterfactuals. (McGinn 1999, p. 16)
As
McGinn acknowledges, he didn’t establish this view. Nor has its denial been
established here. However, once doubts about subjunctives have been assuaged by
securing them in multiverse worlds, they give determinate content to capacity
ascriptions that would otherwise be intolerably vague. To assert that Puck can
be an ass might mean many things, specified by subjunctives about his rude
behavior at parties, his transmogrifying by magic, his wearing a papięr-maché
donkey’s head, and so forth. So the tracking theory’s subjunctives should be
accepted as more fundamental. Capacities are specified by subjunctives, and
subjunctives are grounded in possible worlds.
The
foregoing three-tier reliabilist account of S knows that p leaves
hostages to scientific fortune: the multiverse interpretation of
possible-worlds semantics could turn out to be as imaginary as A Midsummer
Night’s Dream. But a certain vulnerability is becoming in a philosophical
analysis. With reference to integration of knowledge with the multiverse, the
vulnerability reveals a further implication of the analysis: What distinguishes
true counterfactuals from mere fantasy is the grounding of the former in
parallel worlds. If there is no physically possible world in which the liquor
of the flower love-in-idleness, placed upon someone’s brow, causes that person
to madly dote on the next live creature that it sees; then that herb’s powers
are simply Shakespeare’s fancy. If all counterfactuals are similarly bereft of
grounding, we are not knowers; we do not track. What could or might be is what
actually is, and no more. Knowledge is impossible.
The
integration of knowledge and the multiverse has been presented as an
illuminating structure, not as something proven. For all that has been shown
here, it can be viewed as a denial that knowledge is possible as well as a
statment of what knowledge requires. Whatever the wattage of the illumination,
the structure is small. It does not canvas important objections to the tracking
theory such as Christopher Peackocke’s (1986), nor does it scout the prospects
of integration with other forms of reliabilism, such as Alvin Goldman’s
development of it (1967, 1976). The hypothesis for a larger project would be
that distinguishing different methods, along the lines of the reply to McGinn,
would answer objections like Peacocke’s; and that other forms of reliabilism
would integrate readily with tracking and multiverse-possible worlds,
especially those like Goldman’s that bring counterfactuals into the analysis
rather than shunning them in McGinn’s fashion.
REFERENCES
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universal quantum computer", in Royal Society of London, Volume A
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Goldman,
Alvin. 1976. "Discrimination and Perceptual Knowledge", in Journal
of Philosophy, Volume 73.
Goldman,
Alvin. 1967. "A Causal Theory of Knowing", in Journal of
Philosophy, Volume 64.
Lewis,
David. 1986. On the Plurality of Worlds. Oxford: Blackwell.
McGinn,
Colin. 1999. Knowledge and Reality. Oxford: Clarendon Press.
Norris,
Christopher. 2000. Quantum Theory and the Flight from Realism. London:
Routledge.
Norris,
Christopher. 1999. "Should Philosophers Take Lessons from Quantum Theory?
", in Inquiry, Volume 42.
Nozick,
Robert. 1981. Philosophical Investigations. Cambridge, MA: Harvard
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Peacocke,
Christopher. 1986. Thoughts: An Essay on Content. Oxford: Blackwell.
Price,
Michael Clive. 1995. "The Everett FAQ",
http://hedweb.com/everett/everett.htm".
Williams,
Michael. 2002. "Nozick on Knowledge and Scepticism", in Robert
Nozick. Cambridge, MA: Cambridge University Press.
Copyright © 2004 Minerva
All rights are reserved, but fair and good faith use with full attribution may
be made of this work for educational or scholarly purposes.
Wesley Cooper
teaches Philosophy at the University of Alberta, Edmonton.
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