Deflating Existential Consequence:
A Case for Nominalism
If we must take mathematical statements to
be true, must we also believe in the existence
of abstracter--eternal invisible mathematical
objects accessible only by the power of pure
thought? Jody Azzouni says no, and he claims
that the way to escape such commitments is
to accept (as an essential part of scientific
doctrine) true statements which are "about"
objects that don't exist in any sense at
all. If we must take mathematical statements
to be true, must we also believe in the existence
of abstracter--eternal invisible mathematical
objects accessible only by the power of pure
thought? Jody Azzouni says no, and he claims
that the way to escape such commitments is
to accept (as an essential part of scientific
doctrine) true statements which are "about"
objects that don't exist in any sense at
all. This is the first time that Quine's
criterion of ontological commitment is fundamentally
question called into question. Without this
criterion, the modal realism of David Lewis
collapses. For analytic tradition in philosophy
this is a major revisioning of valid argumentation
in metaphysics. Perhaps (sad to say, for
the question of intellectual freedom within
the profession) that it may have been necessary
for Quine and Lewis to die before nominal
view could get a hearing.
Azzouni illustrates what the metaphysical
landscape looks like once we avoid a militant
Realism which forces our commitment to any-thing
that our theories quantify. Escaping metaphysical
straitjackets (such as the correspondence
theory of truth), while retaining the insight
that some truths are about objects that do
exist, Azzouni says that we can sort scientifically
given objects into two categories: ones that
exist, and to which we forge instrumental
access in order to learn their properties,
and ones that do not, that is, which are
"made up" in exactly the same sense
that fictional objects are. He offers as
a case study a small portion of Newtonian
physics, and one result of his classification
of its ontological commitments is that it
does not commit us to absolute space and
time.
Azzouni begins by exaiming the notion of
truth. His view on truth is a fairly deflationary
one: The role of the truth predicate is to
enable us to assent to sentences we cannot
explicitly exhibit. He uses this role of
the truth predicate plus other subsidiary
considerations about scientific theories
to show that applied mathematical doctrine
and empirical laws must be taken by us to
be true. For expository purposes, the discussion
is divided into two parts. In chapter 1,
Azzouni lays out the details about blind
truth ascription and the truth predicate
that, in a broad way, indicate why we are
apt to be committed to the truth of what
is indispensably contained in our body of
beliefs. In chapter 2, he fine-tunes the
issue and evaluates strategies for being
agnostic or fictionalist about applied mathematical
doctrine or empirical law despite its indispensability.
Next Azzouni turns to questions of ontological
commitment. Quine's criterion for what a
discourse is committed to is evaluated and
found wanting. There are, that is, alternatives
that neither Quine nor anyone else has successfully
ruled out. A substantial portion of chapter
3 is dedicated to careful evaluation of Quine's
triviality thesis: the claims that "there
is" is used in the vernacular to indicate
ontological commitment, and that this use
is regimented by the first-order existential
quantifier. The conclusion is that we cannot
say what is the best criterion for what a
discourse commits us to until we first establish
a criterion for what exists.
Azzouni argues that although no philosophical
argument is available to definitively fix
a criterion for what exists, still, it can
be shown that our linguistic and epistemic
community takes something to exist if and
only if it is ontologically independent.
Azzouni attempts to spell out in some detail
what "ontologically independent"
might mean.
Next he discusses how speakers in the vernacular
indicate ontological commitment. The conclusion
argued for is that there are no linguistic
devices, no idioms (not "there is,"
not "exists") that unequivocally
indicate ontological commitment in the vernacular.
Nevertheless, speakers are competent at
recognizing when ontological claims are being
made (provided, of course, that certain people—e.
g., philosophers—avoid being too tricky about
it).
In part II, Azzouni turns to the question
of how the considerations of part I can be
used to evaluate the ontological commitments
of scientific theories. To this end, Azzouni
sorts the posits (quantifier commitments)
of theories into three kinds: thick, thin,
and ultrathin, and distinguishes these on
the basis of the various epistemic requirements
they impose on knowers.
Azzouni argues that we take only thick and
thin posits to be ontologically independent
(and thus to exist). He also discusses ontological
closure conditions, methods in science that
characterize limits on what there is. He
uses the presence of such conditions to argue
for a version of the Eleatic Principle, the
claim that, in some sense, everything there
is has causal powers.
Azzouni describes ways in which mathematics
is applied and gives a number of examples,
the most significant being variants on the
application of Newtonian cohesive-body mathematics,
a mathematical system that codifies a (small)
portion of Newtonian mechanics. Concluding
he turns to the evaluation of the ontological
status of various posits in cohesive-body
mathematics: Azzouni claims that, for example,
despite the presence of spatial and temporal
posits in cohesive-body mathematics, such
posits are ultrathin, and he also asserts
that cohesive-body mathematics is not committed
to forces, either.
Excerpt: Philosophy—at least that tradition
of it I choose to work within—has at best
an uneasy relationship with ontology. Carnap,
notoriously, denied that genuine ontological
questions (and purported optional answers
to these questions) are meaningful, and this
viewpoint is one that continues to be a live
possibility (or at least a serious temptation)
for contemporary philosophers. On the other
hand, Quine's criterion for what a discourse
is committed to is widely (and uncritically)
adopted despite an official disagreement
over what it amounts to, and whether a coherent
version of it is even available.' Careful
attempts to evaluate the criterion itself
are sporadic and rare; conscious and unconscious
reliance on it for one or an-other ontological
project in philosophy of language, philosophy
of logic, philosophy of mathematics, philosophy
of science, philosophy of mind, metaphysics
proper, ethics, and so on is the norm.
Of course I too understand the appeal of
"getting on with it," the somber
recognition that life is short, that getting
to the bottom of things should not mean staying
down there for the rest of our professional
careers. It's easy to think, "let this,
at least, be a fundamental building block
in our philosophical arsenal; let this (at
least) be something our community of philosophers
can hold in common and can use as a common
assumption, as a philosophical paradigm,
if you will; let this (at least) unify us
as a profession as we pursue our various
ambitious metaphysical (or metaphysically
deflating) philosophical projects."
As the last paragraph intimates, the book
you're reading stays pretty near the bottom
of things. Part I of this book evaluates
arguments for Quine's criterion and shows
them wanting. I consider various alternative
criteria and eventually find a way to argue
for one. The argument is detailed—tortured,
even—but (I hope) ultimately convincing.
I argue that Quine's attempt to substitute
a logically prior criterion for what a discourse
commits us to, in place of a more traditional
metaphysical criterion for what exists, is
a sleight of hand. Instead, I find that folk
ontology takes the ontological independence
of something (in a sense to be specified)
as criterial for whether it exists. Accepting
this requires us to overturn Quine's decision
to take the objectual existential quantifier
in a regimented discourse as carrying ontological
commitment, and forces us to adopt a special
predicate designated to carry ontological
commitment instead: an existence predicate.
The famous Quine-Putnam indispensability
thesis takes the indispensability of mathematical
doctrine to scientific practice to imply
(1) the truth of that doctrine, and thus
to imply, via Quine's criterion for what
a discourse is committed to, (2) the existence
of mathematical abstracta. My arguments against
Quine's criterion drive a wedge between
(1) and (2): the truth of mathematical doctrine
(all by itself) doesn't imply the existence
of the abstracta that this doctrine is about.
Traditionally, one of the best arguments
for Platonism has been the truth of mathematics—either
applied or unapplied. And, unsurprisingly,
the standard nominalist response to mathematical
truth has been either to try to show that
mathematical truths aren't (or needn't be)
what they appear to be (they're metaphorical,
say, or they actually have very different
logical forms in which obnoxious existential
commitments to abstracta are missing), or
to try to show that they are, if taken literally,
not indispensable to empirical science (despite
appearances to the contrary), and thus statements
we needn't take to be true.
By contrast, my nominalism steals the best
from both sides in this debate: I take true
mathematical statements as literally true;
I forgo at-tempts to show that such literally
true mathematical statements are not indispensable
to empirical science, and yet, nonetheless,
I can describe mathematical terms as referring
to nothing at all. Without Quine's criterion
to corrupt them, existential statements are
innocent of ontology. (I'll temporarily call
this "the separation of existential
truth from ontology" or, for short,
"the separation thesis.") The separation
thesis results in a rather atypical nominalism,
but I hope the book will show that, despite
this, it's very appealing.
The main advantage of the separation thesis,
overall, is that it simplifies so many metaphysical
tangles. I won't illustrate this generally—there
are too many topics to cover—but I do discuss
(1) mathematical abstracta as they arise
in the application of mathematics to science,
and (2) fictional or nonexistent objects.
I indicate—but hardly in a complete way—the
value of the separation thesis to issues
regarding properties. It proves equally illuminating
to the metaphysics of space and time (I discuss
this somewhat—but there is lots more to
say, e. g., purported problems with presentism).
The separation thesis provides so many simplifications
in meta-physics simply because it eliminates
the need to postulate something as existing
just because certain truths prove indispensable;
many metaphysical entanglements arise because
this is taken for granted. Coupling the separation
thesis with other ways of determining what
exists at long last frees ontology from its
linguistic straitjacket. (E. g., the linguistic
form that fundamental science takes—which
predicates appear in its laws—need not determine
our most fundamental metaphysical commitments.)
Some philosophers have been exploring what
might be called the program of naturalized
ontology, the idea that in science ontological
practices are already in place that dictate
scientific commitments, and that to engage
in "naturalized ontology" is simply
to adopt those practices. I've some sympathy
with this move, and broadly speaking, it's
my escape route from ontological nihilism
to the safety of a particular criterion for
what exists. But there are at least two crucial
ways I break with this approach. First, I
doubt that one finds in science autonomous
practices exemplifying a criterion for what
exists (or a criterion for what scientific
discourse commits us to): Science (I claim,
and I hope) is not as revolutionary as that.
The criterion for what exists operating in
science is drawn from epistemic and ontological
practices at work in the human community
at large—it's a criterion we've adopted in
common. (I say a little more about this shortly.)
Second, I continue to hold that the "ontological
nihilism" of my 1998 is right there
are no philosophically conclusive ways to
argue for our criterion for what exists.
That is, we can imagine alternative communities
with the same science we have but with different
beliefs about what exists because (and solely
because) they have a different criterion
for what exists; they're otherwise unaffected
by their choice. In particular, there is
nothing we can point to, either practically
speaking or in terms of some implicit incoherence
in their practices or theories, that shows
they've got the wrong criterion for what
exists (see chapter 4 for a discussion of
this).
Notice what's required when it's claimed
that there is nothing to adjudicate between
our criterion for what exists and the different
one of the imagined alternative community:
I'm not asking for an a priori resolution
of the disagreement (I don't believe in the
existence of things like that). I'm asking
for some way of being able to show (empirically)
that either we or the members of the alternative
community are worse off be-cause of our (or
their) choice of criterion for what exists—that,
for example, our (or their) scientific or
epistemic practices fall short in some way.
Only then can we say that there is a genuine
issue to be judged rationally.
Unlike the Quinean criterion, which commits
us to everything the objectual existential
quantifier in (regimented) scientific doctrine
ranges over, my criterion is more discriminating.
Each scientific case must be individually
investigated in fair detail to see what it
commits us to and what it doesn't. This is
because when mathematical discourse is applied
empirically, the terms in it (which indicate
abstracta) can play two very different roles:
sometimes they proxy for items that exist,
and sometimes they don't.
As an illustration of this complex and interesting
phenomenon, part II of this book examines
a (small) portion of Newtonian physics. The
point of this application is threefold: first,
to see in a real but relatively straightforward
case how my approach sorts out what exists
from what doesn't; second, to see how ontological
evaluation can yield principled results even
in a context that far outstrips the commonsense
arena that our ontological promptings were
first honed in; and third, to see how powerful
methodological prejudices about explanation
can conspire with routine generalizing practices
in mathematics to produce (when that mathematics
is applied) strong (and yet unjustified)
ontological intuitions. I single out the
substantivalist/relationist debate about
space and space-time as an excellent illustration
of this last phenomenon. I'll show how the
application of geometries to motion that
yields simple and unified laws leads to intuitions
about the existence of absolute space.
In a way, the hope for principled results,
raised as my second aim earlier, brings us
back to Carnap's original motivation for
deflating ontology. What look like bizarre
positions—at least from the commonsense point
of view—are the primary offering in the history
of metaphysics, as even a cursory glance
at that history indicates. Monisms of various
sorts, denials that humans (or any other
macro-object) exist, claims that numbers
exist, that only numbers exist, that fictional
entities exist, that possible worlds exist,
that only atoms exist, that only strings
exist, that time doesn't exist—all such positions
are available to the thrill-seeking ontologist.
(Science fiction isn't half so imaginative
or—according to common sense—off-thewall
as what can be found in the writings of obsessive
ontologists.) Worse, and this is how I read
Carnap's motivation for deflating ontology,
there seems no principled way to decide among
these (competing) positions.
Carnap (1950) famously distinguishes internal
questions from external questions. On the
latter, he writes: "This question [of
the reality of the thing world itself] is
raised neither by the man in the street nor
by scientists, but only by philosophers.
Realists give an affirmative answer, subjective
idealists a negative one, and the controversy
goes on for centuries without ever being
solved".
Carnap's claim that the ordinary person (or
scientist) does not raise ontological questions
is explicitly denied by Kant (1783), who
wrote:
That the human mind would someday entirely
give up metaphysical investigations is just
as little to be expected, as that we would
someday gladly stop all breathing so as never
to take in impure air. There will therefore
be meta-physics in the world at every time,
and what is more, in every human being, and
especially the reflective ones; metaphysics
that each, in the absence of a public standard
of measure, will carve out for themselves
in their own manner.
Kant's own attempt to short-circuit uncritical
ontologizing is hardly straightforward or
easy-going. But I think he was right, both
about what you might call the human instinct
for ontology and about the importance of
care and subtlety in sorting out how that
instinct—and ontology itself—should be treated.
I didn't say so earlier, but even the Quinean
take on ontology, de-spite its apparent rescue
of that subject from the Carnapian limbo
of non-sense,' is as deflationary and in
a sense as dismissive as the Carnapian position
it opposes, at least under a fairly straightforward
interpretation: Ontologizing is a philosophical
practice, and like all philosophical practices,
it's continuous with science. Indeed, modulo
regimentation, what science tells us there
is, is what there is.
But what does science tell us there is? The
recent outpouring of onto-logical posturings
by professional physicists turned lay-ontologists
(for examples of Quine's favorite sort of
scientist) indicates nothing particularly
straightforward or definitive about ontological
readings of science—at least as far as the
professional practitioners of those sciences
are concerned. Is the Schrodinger equation
real? Weinberg thinks so.' Does time exist?
Barbour (1999) thinks not.' Examples can
be multiplied easily. It's hard to believe
that this can be sorted out neatly by regimenting
scientific discourse to see what the quantifiers
of the regimented discourse range over.
Why not?" In part because some genuine
ontological concerns elude the narrower issue
of what the objectual existential quantifiers
in a discourse range over. This is even
true of Quine's own ontological promptings,
his physicalism, for example, which is an
ontological position he takes but that cannot—as
he admits—be represented by what objectual
existential quantifiers range over in the
best regimentation of the scientific discourse
he accepts. To do that successfully, all
nonphysicalistic vocabulary would have to
be eliminated. And Quine admits that this
can't be done."
Concerns with ontology, on the part of ordinary
people, on the part of physicists trying
to interpret the ontology of the wild new
scientific theories they find themselves
committed to the truth of, and even on the
part of a grudging Quine trapped within a
nonaustere web of beliefs, take the form
they've always taken: queries about which
things we should take to exist and which
not; and this is regardless of what our discourse
seems to commit us to.
And let's admit it: For better or worse,
the ordinary person's concern with what there
is and his or her concern with how we're
to read off what there is from what we take
to be true are real concerns just like Kant
said they were, and ones to be treated with
respect. However, as with the more sophisticated
ontologizing that philosophers and physicists
engage in, the implicit methodology that's
actually doing all the work to support both
sophisticated and folk ontological positions
should not be left at the level of unconscious
intellectual reflex or to occasional ritualized
nods to philosophical ancestors, such as
those to the late Quine. Rather, this methodology
should be brought explicitly out into the
open, where we can all participate in the
evaluation of it.
One point about my footnotes. These are used
by many philosophers solely for the purpose
of citation. I don't use them that way—the
reader intent on seeing the force of the
position I offer should read the footnotes
along with the main text. This is why I use
footnotes rather than end-notes. The same
is true, of course, of my previous books.
But I've been told that I should point this
out.
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