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Carnap's ConventionalismAuthor(s): Richard CreathSource: Synthese, Vol. 93, No. 1/2, Carnap: A Centenary Reappraisal (Nov., 1992), pp. 141-165Published by: SpringerStable URL: http://www.jstor.org/stable/20117711 .
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RICHARD
CREATH
CARNAP'S CONVENTIONALISM
When Herbert
Feigl
spoke
at
the memorial
session
for
Rudolf
Carnap
in
1970
he
recalled
an
incident
that
was
especially
revealing:
he
and
Carnap
were
walking in
a
park in Vienna, and Carnap described the
first ideas that later became The
Logical
Syntax of
Language.
Feigl
responded
that the
syntax
that
Carnap
formulated
in
a
metalanguage,
amounted
to
a
'Hilbertization'
of
Principia
Mathematica .
Carnap
smiled and
accepted
this
description
as
essentially
correct
(Feigl,
1975,
p.
xvi).
Feigl
was
right,
of
course,
perhaps
righter
than
he knew. For
the
Logical
Syntax
owed far
more
than its
metamathematical form to Hil
bert. The
book's central
idea is
an
epistemic
doctrine that
shaped
Carnap's
philosophy
until the
day
he
died. And that central
idea is
a
development of Hubert's work as well. Ironically this Hilbertization of
content
beyond
that
of
form
probably
did
not
occur
until
the
syntax
project
was
well under
way,
and
hence
was
probably
not
part
of
the
sketch
that
Carnap
presented
to
Feigl.
But who knows?
Perhaps
that
crucial
epistemic
doctrine
was even
then
forming
in
the back of
Carnap's
mind.
Could that be
why
he smiled
at
Feigl's
remark?
In
any
case
what I
want to
do
here
is
to
explore
that
epistemology
of
Carnap
in
order
to
see
what it
was,
why
it
was
such
a
step
forward
in the
1930s,
and what it has
to
teach
even now.
To
do that
my
remarks
will
divide into three
parts.
In
the first
I
shall
sketch
Carnap's
new
epistemology;
in the second I shall
say
something
of its
sources;
and in
the
third,
after
some
brief remarks
about
methodology,
I
shall
try
to
apply
the view
to
some
enduring problems
of observation.
1. CARNAP'S
EPISTEMOLOGY
One
tends
to
think of
Carnap
as a
well-known
figure,
but
if
those
paragraphs
on
logical
empiricism
that
are
apparently
de
rigueur
in
recent
philosophy
of science books
count
as
evidence of the
received
view of
Carnap's epistemology,
then
most
philosophers
have
only
a
Synthese
93:
141-165,
1992.
?
1992 Kluwer Academic Publishers. Printed
in
the Netherlands.
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RICHARD CREATH
hazy
idea of
Carnap's
work,
and their criticisms
are
often
directed
against
a
straw
man.
We would do well
to
begin
afresh.
The chief business of
epistemology
is
to
provide
a
theory
of
justifi
cation;
it
must
tell
us
what beliefs
are
justified,
and in
what
manner
and
to
what
degree they
are so.
Usually
when
we
are
asked
to
justify
our
beliefs
we
do this
by
giving
reasons: we
bring
forward
one
or more
other beliefs
which
(1)
are
themselves
justified,
and
(2)
stand in the
right
sort
of
relation
to
the belief for which
justification
was
sought.
Both features
are
important.
It is the
special
province
of
logic,
deductive
and
inductive,
to
specify
further
the
second
requirement.
But it
is the
first
requirement,
that
the
justifying
beliefs
themselves be
justified,
that
concerns
us
at
this
moment.
Assuming
that
justification
is
not to
be
circular,
that first
requirement
involves
us
in
a
regress
which,
if
it is
not to
be
vicious,
must
stop
somewhere.
In
other
words,
if
reason-giving
is
to
succeed
in
justifying
anything,
there
must
be
some
beliefs
which
are
justified
in
some
way
other than
inference;
there
must
be
some
non-inferentially
warranted
beliefs. This fact is quite separate from any issue between foundational
ist and coherentist
epistemologies.
It is
generally
conceded
that
one
such alternative mode of
justification
is observation.
We
may
set
aside
questions
of whether
one
observes
physical
objects
or
one's
own
interior
(mental)
states
or
both. Whatever
the
content
of observation
might
reasonably
be taken
to
be,
observation
cannot
by
itself be sufficient
to
generate
either what
we
think
we
know
or even
any
useful
body
of
justified
belief
at
all. This
is due
chiefly
to
the
fact that
we
cannot
observe
the
validity
of
any
principle
of
inference,
and
without inference
even
certainty
within
the observational domain
will not
carry
us
very
far. There are also other reasons for
doubting
the
sufficiency
of observation.
In
some
cases,
such
as
mathematics and
set
theory,
the
objects
are
not
of
a
sort
to
be
observed.
Moreover,
even
where the
objects
in
question
are
observable,
the claims
to
be
justified
may
be such that
they
cannot
be
justified
on
the
basis
of observation
or
else
cannot
be
justified
to
the
requisite
degree,
i.e.,
to
the
degree
that
we
generally
believe that these
beliefs
are
justified.
In this latter
category
might
fall,
not
only geometrical
beliefs,
but also beliefs about
the causal
structure
of the
world,
and
certain
other 'fundamental'
be
liefs,
such
as
that red
is
a
color and that
nothing
is both
red
and
green
all
over
at
the
same
time.
Indeed,
many
if
not most
of the claims of
interest
to
philosophers
fall
into
this
category.
Consider
especially
a
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CARNAP'S
CONVENTIONALISM
143
belief
that observation is
to
be
trusted. How could this be
justified
on
the basis
of
observation
alone without
begging
the
question
at
issue?
If
observation alone
is
not
enough
to
initiate
a
suitable
body
of
justified
belief,
where else
can we
turn?
Russell's
answer
is
straightfor
ward:
we can
and
must
rely
on
direct
metaphysical
intuition,
though
he tends
to
call it direct
acquaintance (Russell,
1912,
p.
105).
Axiomat
izing
a
body
of belief is useful because it reveals which
beliefs
rely
(for
their
justification)
on
which
other
beliefs. But
axiomatization does
not
tell
us
how
the
axioms
are
justified;
at
best
it
reveals
which beliefs
are
in
need of
a
special
mode of
justification.
Where
our
beliefs
concern
principles
of
inference,
mathematics,
logic,
or
universals
more
gen
erally,
observation
cannot
sufficiently
warrant
the axioms and hence
cannot warrant
the
rest
of
our
beliefs which
depend
on
those
axioms.
We do have such
knowledge,
so
it
must
rely
on
intuition
-
there is
no
alternative.
This
Russellian
epistemology
is
worse
than
a
crime,
it is
a
blunder.
There
is,
for
example,
wide
disagreement
among
intuitions
concerning
the existence and character of universals. There is, unfortunately, no
plausible
way
to
resolve such
disagreements,
and
some
intuitions,
such
as
those
underlying
naive
set
theory,
are
flatly
contradictory.
Even when
intuitions
coincide,
such
as
in
mathematicians'
intuitions
concerning
arithmetic,
this
coincidence
is
more
readily
explained
by similarity
of
training
than
by
intuitions which
are
independently
reliable. In
this
respect,
the
matter
is
like
explaining
the coincidence
of beliefs
on
the
Trinity
among
Anglican
bishops: presumably
the
best
explanation
would
stress
the
efficiency
of the
seminaries rather than
a
happy
reiter
ation
of divine
revelation.
In
mathematics,
no
less than in
religion,
intuitions
diverge
with differences in
time,
training,
and
culture,
as well
as
in
more
idiosyncratic
ways.
The
situation is
actually
worse
than
this.
Even
if
intuitions
agree,
they
need
not
be
right,
and
even
if
some
of
them
are
right,
then in
general
there neither would
be
nor
could be
an
explanation
of this
phenomenon.
To
see
why,
contrast
the
case
of
intuition
with
ordinary
observation. The
story
that observation
supports
includes
an
explana
tion of
how
it
is,
say,
that
in
certain
circumstances
a
certain
paper's
being
white
can
bring
about
a
belief that
that
paper
is
white.
Such
explanatory
stories
are
still
rather
sketchy (though
they
are
being
fleshed
out
more
and
more)
and
even
if
complete
would
not
prove
the
truth
of
our
observational
judgments.
But
our
stories of the world
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RICHARD CREATH
would be
poorer
without such
explanations,
and
Russell has
no
even
sketchy
account
of
why
intuitions would be
likely
to
be
correct.
Nor,
of
course,
does
anyone
else.
Where the
intuitions
concern
objects,
such
as
numbers,
which
are
said
not
to
be in
the causal
order
(or
alternatively
not
in
space
and
time),
it
is difficult
to
imagine
how
there
even
could
be
an
explanation
for
intuitions
corresponding
to
our
explanations
of
the
reliability
of
ordinary
perceptual judgments.
This
dissimilarity
be
tween
so-called mathematical
intuition and
ordinary perception
is
one
of the
chief
roadblocks
in
the
way
of such writers
as
G?del,
who would
attempt
to
assimilate mathematical
intuition
to
homely
observation.
In
the face
of
all these difficulties the
only
defense
for
metaphysical
in
tuition
is
precisely
the
one
that
Russell offers:
metaphysical
intuition
must
be
a
source
of
justification
because there is
simply
nothing
else
that
can
provide
the
required
warrant.
Russell is driven
to
intuition
by
the
lack of
a
satisfactory
alternative.
Carnap
was
militantly
opposed
to
the
idea that intuition could be
a
source
of
justification,
though
this
opposition
was
expressed
as a
rejec
tion of metaphysics. Metaphysics, according to Carnap, was a suppos
edly
trans-empirical
access
to
a
domain of
supposititious
entities
or
to
mysterious
features
of
ordinary objects,
features
beyond
the reach
of
justification
based
on
observation
(Carnap,
[1932a]/1959,
pp.
76-77;
Carnap,
1935,
p.
15).
Carnap's
rejection
of
metaphysics
is well
known.
Less
widely
discussed
is
the fact that the elimination of
metaphysics
specifically
includes
the elimination of the
direct
metaphysical
in
tuitionism that Russell embraced.
An
explanation
of
why
Carnap
was
so
indirect in his
rejection
of
Russell's intuitionism would call for
a
study
of
the
personal
rather
than
the scientific relations
between
these
men.1 At
any
rate, Russell's solution is not
open
to
Carnap.
Against
this
background
Carnap
made
a
refreshing
and
welcome
suggestion:
the axioms
can
be
construed
as
definitions
(implicit
defi
nitions)
and
their assertion
as
commitment
to
a
language containing
the
terms
so
defined. The axioms
or
postulates
need
no
further
epistemic
justification
because
a
language
is neither
true
nor
false,
and
one
is
free
to
choose
a
language
in
any
convenient
way.
If
someone
else should
choose
other
apparently
conflicting
postulates,
there is in fact
no
dis
agreement
because
each
postulate
set
is
constitutive of the
concepts
it
employs,
and hence
the
one
body
of
postulates
is
not
denying
what the
other is
asserting.
In
this
manner
the
postulates
are
not
even
intended
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CARNAP'S
CONVENTIONALISM
145
to
reflect
an
antecedently
and
independently
existing reality,
but rather
literally
to create
the
claims
they
express.
It
may
be
that
some
postulate
sets
are
better
than others.
But
the
'betterness'
in
question
concerns
their
practical
usefulness:
some
are
more
powerful
or
easier
to
use
than others.
In
terms
of
epistemic
justification
or
cognitive
warrant
they
are
all
on
a
par.
Indeed,
they
are
the 'meter
sticks' for
the
justification
of
anything
else.
Epistemically
the
choice
among
them is
conventional, though
the
constraints
imposed
by
pragmatic
utility
can
be
significant.
For
example,
an
inconsistent
postulate
set is
not
very
useful.
For
most
logicians
of the
period,
includ
ing
Carnap,
every
sentence
as
well
as
its
negation
would
trivially
follow
from
a
contradiction.
An inconsistent
postulate
set
would therefore
fail
to
draw
any
cognitively
interesting
distinctions
among
sentences
or
beliefs.
Though
the
preference
for consistent
systems
is
treated
as a
pragmatic
one,
the
pragmatic
considerations
are
powerful
indeed.
Even
so,
just
because
a
postulate
set
includes
as
consequences
some
sentence
and
that
sentence
preceded
by
a
'-i',
the
postulate
set
is
not
thereby inconsistent. The sin , as Quine would later put it, would at
most
be
against
the
ordinary
(logicians')
use
of the
'?i'.
The
postulates
would constitute
implicit
definitions
of the
symbols
involved,
but the
sense
thus
constituted
for the
'-i'
would
not
be that of
negation (Quine,
1936,
p.
90).
This
suggests
another
sense
in which alternative
postulate
sets
can
be
compared:
some
will
provide
explications
of
ordinary
concepts
while
others
will
not. I shall
not
enter here
into
a
technical
discussion
of
the
demands
on an
adequate
explication
(Carnap,
1950,
pp.
5-8),
but
suffice
it
to
say
that
if the
postulates
(construed
as
implicit
definitions
of the terms
they contain)
assign
meanings
which are
sufficiently
close
to
the
meanings
that these
terms
ordinarily
enjoy,
then the
postulates
can
be
thought
of
as
providing
a
clarification of and
hence
an
explication
of those
ordinary
concepts.
There
are
sometimes
reasons
of intellectual
economy
for
wanting
explications
of
familiar
notions,
but
the failure
to
provide
such would
not
by
itself be
a
defect.
After
all,
the novel
concepts
may
in
point
of
practical
utility
be
equal
or even
superior
to
the
ordinary
ones.
This
discussion
of
pragmatic
usefulness and
explication
must not
obscure,
however,
the
epistemic
core
of
Carnap's
doctrine.
The
choice
among
alternative
postulate
sets
is
epistemically
arbitrary;
the
choice
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146
RICHARD CREATH
is
a
matter
of
convention.
Moreover,
the
postulates
themselves
are
the
fundamental
epistemic
doctrine. This fact
is
easily
obscured
even
by
Carnap's
own
way
of
putting
his view.
Carnap
did
not
like the word
'epistemology'
-
it smacked
of
psychology.
So,
he avoided
it.2
Writers,
then
as
now,
often
ran
such
empirical
topics
as
the
qualitative
character
of inner
experiences
or
habits of their association
together
with
the
more
properly philosophic
questions
that
Carnap
wanted
specifically
to
isolate. Instead of
'epistemology', Carnap preferred
the
word
'logic'.
This
break
with tradition is
important,
and it is
signalled by
a
termino
logical change.
But there is still
a
point
to
be
made
in
calling
the
new
logic
epistemological.
Remember that this
logic
was
to
replace
traditional
epistemology
within
philosophy.
It
was
to
tell
us
what is
observable
and what
may
be
inferred from what.
This
is the
pure
structure
of
an
epistemology,
and
it
is
the
purely
structural character
of the
enterprise
that
Carnap
highlights
with the word
'logic'.
Indeed,
when
Carnap's
logic
is
generalized
to
include inductive
logic,
the
re
lation
sought
is that of
confirmation,
a
relation which is
transparently
epistemological. Finally, if we are ever to give empirical meaning to
the notions
of this
logic,
we
must
look
to
community
practices
of
justification.
For
all
of these
reasons
we
must
recognize
the
enterprise
as
epistemological.3
That the choice
among
postulate
sets
is
a
matter
of
convention
is
made
plausible
by saying
that the
postulates
implicitly
define the
terms
that
they
contain. The
definitions
are,
of
course,
partial;
in modern
terminology they
reduce the
family
of models while
imposing
only
very
loose restrictions
on
the
extensions
of
the
terms
involved.
But
even
such
partial
definitions
are
sufficient
to
guarantee
that all of the theorems
are
true in each of the models.
There is also
a
further
consequence
of
calling
the conventions
linguis
tic.
When
we
refer
to
someone's
belief that Finland
is
forested,
the
that-clause
describes the
belief
in
terms
of
a
certain sentential
structure.
Thus,
when
Carnap
says
that the conventions endow
the
sentences
with
meaning
and
provide
the
identity
conditions
for what is
expressed
thereby,
he could likewise
have said that those conventions
provide
the
identity
conditions
for
beliefs.
That
a
belief
is
to
be
justified
in
such
and
such
ways
is what
makes it the
belief
that
it is. If the
system
of
justification
were
altered
it would
no
longer
be the
same
belief. Thus
when
we
refer
to
a
specific
belief,
we
implicitly
refer
to
the
system
of
justification
which constitutes
it.
Carnap's approach
here
is in marked
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carnap's
conventionalism
147
contrast
to
those who would
identify
a
belief
simply
as
a
disposition
to
utter
a
certain
sequence
of
words,
independently
of
how
those beliefs
are
to
be
justified.
Obviously,
this
feature
of the view will have
impor
tant
consequences
for the issues of
skepticism
and
of the
objectivity
of
belief.
At
this
point
it
would be well
to
say
a
bit
more
about
convention,
for it is
not
always
clear what is
at
stake
in
saying
that
something
is
a
matter
of convention
(Quine, 1936). Plainly,
when
Carnap speaks
of
the semantic and
epistemic
features of
our
language
as
conventional,
he does
not
mean
to
suggest
that
they
are
the
products
of
some
actual
legislative assembly
convened
in
antiquity.
But
shorn
of such
unhelpful
metaphor,
what does
conventionality
come
to? The
answer,
in
essence,
is that
to
lay
down
a
linguistic
convention
is
to
adopt
a
certain scheme
of
justification.
This scheme involves
two
specific
features:
first,
there
are
alternatives
to
certain
aspects
of the
justificatory
system;
and,
sec
ond,
the
choice
among
these alternatives
is
arbitrary
in
the
sense
that
no
justification
is
required
for the choice.
In
particular,
to
say
that
postulates are laid down by convention commits one to the idea that
there
are
alternative
postulates
that
could
have
been
chosen,
but
were
not.
It commits
one
likewise
to
the
idea
that
no
further
epistemic
justification
for the choice of
postulates
is
required.
Conventions
are
not
designed
to
reflect antecedent and
independent
facts;
if
they
were
thus
designed
one
would
have
to
show that
they
had done
so.
Rather,
the
postulates
(together
with
the other
conventions)
create
the truths
that
they,
the
postulates,
express.
Calling
the
choices conventional also
reminds
us
that
they
are
r?vis
able.
Again,
to
say
that
something
is conventional is
to
say
that there
are alternatives. That no further
justification
can be
required
for the
postulates
should
not
be
taken
to
suggest
either that
they
are
unrevis
able
or
that
as a
matter
of fact
we
are
unlikely
to
revise
them. We
can
and do
constantly
adjust
our
conceptual
system
in order
to
maximize
its usefulness. Such
revisions, however,
would
not
be
cases
where
a
given
claim
was
first believed and later disbelieved.
In
abandoning
a
postulate
the
system
of
justification
is revised and therewith the
identity
conditions for the belief.
The
words
may
not
have
changed
between
the
postulate
and
its
apparent
denial,
but
their
significance
has.
Carnap
embraced various conventionalist views from his earliest writ
ings,
but
it
was
not
until The
Logical
Syntax
of
Language
that
the
full
theory
appeared.
Until
then he
seemed
to
be
looking
for the
correct
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148
RICHARD CREATH
logical
system
or
the
correct
construction of the
world.
Indeed,
in
an
early
version
of
Logical
Syntax
this
was
still the
case.
The
fully
conventionalist
theory
described above
and
hereafter
appeared
with
the
Principle of
Tolerance:
It
is
not
our
business
to
set
up
prohibitions,
but
to
arrive at
conventions.
. . .
In
logic,
there
are
no
morals.
Everyone
is
at
liberty
to
build
up
his
own
logic,
i.e.,
his
own form of
language,
as he wishes. All that is
required
of him is that, if he wishes to
discuss
it,
he
must
state
his methods
clearly,
and
give
syntactical
rules instead
of
philo
sophical
arguments.
(Carnap, [1934J/1937,
pp.
51-52)
Of
course,
in
saying
that
in
logic
there
are no
morals
Carnap
is
not
denying
the
normative
force
of
logic.
Rather,
he
is
emphasizing
that
there is
no
one
uniquely
correct
normative
story
to
be told.
When
constructing
an
artificial
language,
one
begins
as
above
by
laying
down
conventions which determine
how
various claims
may
be
justified.
When
we
study
natural
languages
the
connection
goes
in the
other direction: evidence about what the conventions are lies in how
various beliefs
are
justified
(Carnap,
1950,
p.
37).
Of
course,
it is
no
easy
task
to learn what claims
are
taken
to
justify
what
other
claims
and
thereby
to
discover what the
principles
of
inference
are
and
what
claims,
if
any,
need
no
further
justification.
Here,
too,
the
claim of
conventionality
consists
in
the
dual
thesis
that there
are
alternatives,
i.e.,
that the
system
of
justification might
have been otherwise
con
structed,
and
that the chosen alternative needs
no
further
justification.
That the
conventions
constituting
the
system
of
justification
are
at
bottom
arbitrary
poses
no
threat whatever
to
the
objectivity
of the
postulates
and their
consequences.
This was of
particular
concern to
Carnap
because
he
thought
that all
of
logic
and
mathematics,
insofar
as
the
claims
thereof
can
be
assessed
at
all,
is
to
be
justified
as are
postulates
and their
consequences.
Once
a
system
of
justification
is
chosen,
i.e.,
once
the various
terms
of the
language
are
given
a
definite
sense,
it is
a
completely
objective
matter
whether
B
is
a
consequence
of A. It in
no
way
depends
on
what
any
person
may
happen
to
imagine,
think,
believe,
or
know about these
sentences
(Carnap,
1950,
p.
38).
It is likewise
a
completely
objective
matter
whether
or
not
a
given
claim
needs further
justification.
These
things
are
no
more
subjective
than
the truth
value
of the
claim All
swans are
white ,
given
of
course
that
the
meanings
of the
terms
are
fixed.
If
the
word 'white' has
a
sense
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CARNAP'S
CONVENTIONALISM
149
different
than it in fact
does,
then
the
truth value of the claim
might
be
different,
but
this
in
no
way
impugns
the
objectivity
of All
swans are
white .
Whatever its
truth
value,
it does
not
depend
on our
believing
it
to
be
so.
Carnap's
epistemology
as
I
have
presented
it
so
far
has
a
number of
significant advantages.
It
provides
a
way
of
resolving
foundational
de
bates in
logic
and mathematics. It is
no
longer
necessary
to
worry
whether, say,
Brouwer's
intuitionism
or
classical
mathematics
is the
correct
mathematical
system
(Carnap, [1934J/1937,
p.
305).
Each
can
be construed
as a
separate
proposal
for
structuring
language,
in
short
as
a
system
of
implicit
definition. Each
can
be understood
and
its
practical
consequences
noted. The
proposals
do
not
conflict
with
one
another
so
the foundational debate
can
end.
It
is
similarly
an
advantage
that the
system
provides
an
epistemology
for mathematics
which
ac
cords
well with
our
ordinary
convictions about
how
to
justify
mathema
tical claims: the
justification
of theorems
involves
deriving
them
from
axioms;
their
justification
is
independent
of
experience
and
not
subject
to experimental disconfirmation; and the theorems are objectively true.
That
Carnap
is able
to
achieve all this
without
venturing
into
the
quagmire
of
metaphysical
intuitions
represents
a
tremendous advance
over
the
previously
described view
of
Russell. The
conventionality
at
stake
in
Carnap's epistemology
turns out to
be
a
virtue,
and it is
one
to
which
we
shall have
reason
to return
a
little later in
this
paper.
In
the meantime let
us
look
more
closely
at
the
historical
antecedents of
this conventionalist
and
pragmatist
theory
of
knowledge.
2. carnap's
SOURCES
The
prevailing
view is
that
Carnap's philosophy
comes
directly
from
the work of
Frege
and
Russell.
If
I
am
right
that conventionalism and
pragmatism
are
at
the heart of
Carnap's philosophy
from about 1932
onward,
then that
prevailing
view
is
very
misleading.
To be
sure,
Car
nap
studied
at
Jena with
Frege,
and he
came
away
not
only
with
a
love
of
logic
but also
with
Frege's
intense
anti-psychologistic
convictions.
But
as
we
shall
see
in
a
moment
Frege
was
hardly
an
epistemologist,
and the views he did
hold
were
the
exact
antithesis of
Carnap's.
Russell
by
contrast
did
care
about
epistemology,
but
he
was
also
an
out-and
out
metaphysician
(even
if
Carnap
could
never
quite
admit
the
fact).
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150
RICHARD CREATH
As
we
have
already
seen,
the whole
point
of
Carnap's philosophy
was
to
reject
intuition of
a
Russellian
sort.
So,
where
does the
core
of
Carnap's
epistemology
come
from?
The
kernel
of
the
idea
of
implicit
definition has
been around for
a
long
time.
It
goes
back
at
least
to
the work of
Gergonne
at
the
beginning
of the nineteenth
century
(Quine,
1936,
p.
81n.).
At
the
end
of that
century
definition
was
the
subject
of
two
famous debates: Russell
vs.
Poincar?,
and
Frege
vs.
Hilbert.
In
these,
Poincar? and Hilbert
had
defended
forms of
implicit
definition,
while Russell and
Frege
had
attacked
it. Here
I want to
examine the latter of the
two
debates. There
are
two
chief
reasons
for this.
First,
it shows how
enormously
difficult
it
sometimes
is,
even
for
someone
of
Frege's
perspicacity,
to
grasp
the
idea of
a
set
of
axioms
defining
the
terms
they
contain and thus in
a
sense
creating
the truths
they
express.
Second,
a
review
of
this
earlier
episode
will
show
the
magnitude
of
the shift that
Carnap
is
undertaking,
not
only
from
Frege
and Russell but
as we
shall
see even
from
Hilbert.
Carnap's
view
is
a
descendent
of Hubert's. But it
is also much
more;
for the notion of implicit definition is expanded to cover all of philos
ophy
and
to
provide
the
source
of
meaning
in
physics
and
ordinary
life
as
well
as
geometry
and
mathematics.
The
Frege-Hilbert
controversy
appears
in
their
correspondence
be
tween
1895
and
1903
(Frege,
1980,
pp.
31-52).
The
tone
of their
letters
is
quite
remarkable. The usual stock
phrases
of academic
politeness
aside,
they
are
not
friendly
letters.
It
is worth
noting
that while
Frege
was
the older
man
he
held
a
lesser
position
at
a
lesser
university.
In
fact,
Edmund Husserl
wrote
in
1936:
I never got to know G. Frege personally, and I no longer remember the occasion for
our
correspondence.
At the time he
was
generally regarded
as an
outsider who had
a
sharp
mind but
produced
little
or
nothing,
whether
in
mathematics
or
in
philosophy.
(Husserl,
in
Frege,
1980,
p.
61)
At the time
of
Husserl's
correspondence
with
Frege,
or
at
least the
second
part
of
it,
Husserl
was
Hubert's
colleague
in
G?ttingen
and had
seen
the
Frege-Hilbert correspondence.
By
contrast
with
Frege,
Hil
bert
was
at
the
peak
of his
career,
and he could
legitimately
claim,
along
with
Poincar?,
to
be
one
of the
two
greatest
mathematicians in
the world. It
was
not
until the 1940s
that
Frege's
reputation
among
logicians
rose
to
the level of Hubert's
among
mathematicians.
Frege
began
the
correspondence
by
explaining
his view
on some
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CARNAP'S
CONVENTIONALISM
151
minor
issues from
a
previous
conversation with Hilbert.
Hilbert
politely
replied
that
there
was no
difference
of
opinion
between them.
A few
years
later
Frege
wrote
again,
claiming
that
Hilbert's Foundations
of
Geometry
was
unclear
in
crucial
respects:
Here the
axioms
are
made
to
carry
a
burden that
belongs
to
definitions.
To
me
this
seems
to
obliterate the
dividing
line
between
definitions
and
axioms
in
a
dubious
manner,
and beside
the old
meaning
of
the word
'axiom',
which
comes out
in the
proposition
that
the axioms
express
fundamental facts of
intuition,
there
emerges
another
meaning
but
one
which
I
no
longer quite
grasp.
(Frege,
1980,
pp.
35-36)
Note that
for
Frege
the
axioms
express
intuitions.
What
Frege
says
he
does
not
quite
grasp
was,
of
course,
the whole
point
of
Hilbert's
enterprise.
To
Frege
the
problem
was
worse
than the lack of
complete
clarity.
For
him,
one
must
understand
the
concepts
completely
before
one can
entertain
any
propositions
or
consider
any
as
axioms.
Only
after
we
understand
the
concepts
and
propositions
can
we
ask of
a
given
proposi
tion
whether
its
truth
depends
on
the truth of
any
other
proposition.
In
this
way
we
trace
that
truth
dependence
back
to
those
propositions
(the axioms)
which do
not
rest
on
any
others.
Naturally,
definition
is
permissible;
but definitions
are
merely
devices
of
abbreviation.
Abbreviatory
definition, however,
presumes
that
some
terms
(the
primitives)
already
have
meaning.
Oddly,
therefore,
Frege
went
on
to
insist
that all
terms
in
our
propositions
be
fully
defined,
apparently
in
this
abbreviatory
way.
That
is
just
not
possible.
On
Fre
ge's
account
how
one
learns
the
meanings
of the
primitive
terms
must
remain
forever
an
utter
mystery.
Once
we
do learn the
meanings,
how
do
we
learn
which
propositions
are
true? Our
knowledge
of
the theor
ems
flows
through
inference from
our
knowledge
of the axioms.
But
our
knowledge
of
the
axioms
is
quite
different
(and
I
might
add
also
mysterious).
In
speaking
of
geometry
Frege
says:
I call axioms
propositions
that
are
true
but
are
not
proved
because
our
knowledge
of
them
flows from
a source
very
different from the
logical
source,
a
source
which
might
be
called
spatial
intuition. From the
truth
of the axioms it
follows
that
they
do
not
contradict
one
another. There is therefore
no
need
for
a
further
proof. (Frege,
1980,
p.
37)
Hilbert's whole
program,
or
at
least
the central
part
of
it,
had been
to
prove
the
consistency
of
various
groups
of axioms
or
as
a
part
of
this the
independence
of
various axioms
(i.e.,
the
consistency
of
a
given
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152
RICHARD
CREATH
axiom
as
well
as
of its
negation
with
a
given
group
of other
axioms).
Frege
was
here
suggesting
that this main
body
of Hilbert's
work
was
quite
unnecessary
because
the
truth
of the axioms
could
be
determined
directly
by
intuition and
thereby
the
mutual
consistency
of the
various
axioms
could
be established
effortlessly.
If
Hilbert
was
not
annoyed
by
this dismissal
of his
work,
Frege's
tone
toward the end
of the letter
would
have been
sufficiently
irritating.
What
Frege
said
was:
I
would
not
regard
your
work
as
a
valuable
one
if
I
did
not
believe I could
see
roughly
how such
objections
could be rendered
harmless;
but this will
not
be
possible
without
considerable
reshaping.
(Frege,
1980,
p.
38)
Such
a
tone
would
have
been
more
appropriate
in
addressing
a
graduate
student
than the
most
prominent
mathematician
in
Germany.
Hilbert
did
reply,
however,
and his letter
covers
four basic issues.
First,
meaning
is
given by
the
totality
of
axioms.
Hilbert
is,
in
effect,
a
meaning
holist.
Second,
the
only
thing
one
can
do
to
give
the
meaning
of
a
primitive
term,
such
as
'point',
'line',
etc.,
is
to
give
axioms;
anything
else is
fruitless,
illogical,
and futile .
Third,
Frege's
point
that
first
we
know the truth
of
the axioms
and then
infer
their
consistency
has
the
matter
exactly
backwards.
Fourth and
finally,
of
course
definition
via
a
set
of
axioms does
not
irrevocably
fix
reference,
but that is
perfectly acceptable.
It
does, however,
fix
enough
of the
meaning
for
the mathematical
purposes
at
hand.
One
senses
from this letter
of Hilbert that
he
is
fundamentally
at
cross-purposes
with
Frege,
and
Frege's
long
reply
reinforces
this
view.
Frege
still does
not
understand
the
central
idea of
implicit
definition.
Frege
goes
on
to
raise
several
objections,
one
of which is
important
and
deserves
a
reply.
Hilbert
never
did
provide
such
an answer.
While
there
are
several
later letters
in the
Frege-Hilbert correspondence,
none
is
really
substantive,
and neither
man
felt
compelled
to
alter his
view. Hilbert
said he
was
too
overburdened
with work
to
make
any
detailed
reply,
and the
correspondence
ended
with
an
unpleasant
letter
from
Hilbert:
Many
thanks
for the second
volume of
your
Basic
Laws,
which
I find
very
interesting.
Your
example
at
the end of the book
(p.
253)
was
known
to
us
here;*
I found other
even more convincing contradictions as long as four or five years ago; they led me to the
conviction
that traditional
logic
is
inadequate
and that the
theory
of
concept
formation
needs
to
be
sharpened
and refined.
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carnap's
conventionalism
153
*I
believe Dr Zermelo
discovered it three
or
four
years
ago
after
I
had communicated
my
examples
to
him.
(Hilbert,
in
Frege,
1980,
p.
51)
If
this
deprecation
of
Frege's
work
were
insufficient
to
annoy,
Hilbert
added
an
invitation:
It
is
a
pity
that
you
were
neither
in
Cassel
nor
in
G?ttingen;
perhaps
you
will
decide
to
visit
G?ttingen
between
terms.
Since
rail
travel
is
so
comfortable
today,
personal
communication is surely preferable to the written kind. I at least lack time for the latter.
There
are
a
number of
younger
scholars here interested
in
the 'axiomatization of
logic'
(Hilbert,
in
Frege,
1980,
p.
52)
Such
an
'invitation'
to
travel
away
from the
provinces
in
order
to
talk
with the
junior
faculty
and
graduate
assistants
can
hardly
have
appealed
to
Frege.
It
is
not
surprising
that there
were
no
further letters between
the
two.
What do
we
learn from all
this
(besides
the facts
that
great
logicians
do
not
always
understand
alternative
points
of view and that
neither
great
mathematicians
nor
great logicians
are
uniformly very pleasant)?
We
learn,
first,
that there
was a
precedent
for the
central
conven
tionalist
core
of
Carnap's philosophy.
Second,
this
precedent
is
not
to
be found
in
the
Frege-Russell
tradition from
which
Carnap
is
usually
thought
to
arise,
but rather
in
the tradition
that
Frege
and
Russell
attacked
(often bitterly).
Third,
Carnap
went
considerably
beyond
Hil
bert. Neither in the
correspondence
with
Frege
nor
anywhere
else did
Hilbert
give
any
hint of
Carnap's
theory
of
pragmatic
constraints
on
convention. Nor does Hilbert
give
any
general theory
of
analyticity.
Moreover,
Carnap
greatly
generalized
the
theory
of
implicit
definition.
Not only did he extend it to all of logic, mathematics, and philosophy,
but
as
we
shall
see,
he extended its relevance
to
the
concepts
of
empiri
cal science
as
well.
In
this
respect
particularly,
Feigl's
remark that
Carnap's
work
amounts
to
the Hilbertization of
the
language
of science
is
especially prescient.
3.
EXTENDING THE STORY TO
SCIENCE: METHODOLOGY
In
describing
Carnap's
conventionalism
and
pragmatism
I
have
spoken
thus
far
of axioms and definitions
in
a
way
appropriate
to
mathematics
and other
very
abstract
domains. These
are
domains of
our own
making,
and insofar
as
claims
concerning
these domains
are
acceptable,
it is
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154
RICHARD CREATH
because
our
postulates
have made them
so.
In
contrast,
Carnap
thought,
the
world
of
empirical
science
is
not
wholly
of
our own
making,
and
one
of
Carnap's
chief aims
in
framing
his
epistemic
view
was
to
provide
an
account
of
our
knowledge
of the external world.
So
far,
however,
no
provision
has
been
made in the
story
either
for scientific
methodology
or
for observational
knowledge,
and
to
this
we
must
now
turn.
As
we
shall
see,
implicit
definition
by
the
epistemic
structure
is
still
an
important part
of
Carnap's approach. Moreover,
the
epistemic
structures
are
to
be laid down
by
convention
and
justified only
by
the
pragmatic
utility
of
doing
so.
Finally,
we
shall
see
that
despite
this
Carnap
is
no
advocate of unbridled conventionalism
in
a
way
that
would
threaten the
objectivity
of
our
scientific
beliefs
about the world.
There
is much
to
be said about scientific
methodology,
but here
I
want to
make
only
a
few
very
brief
remarks
so
that
I
can
leave
more
room
for
methodology's
much
neglected
cousin,
observation. Even
these brief
remarks
will
be
restricted
to
a
single
topic:
induction.
We
have
already
seen
that
Carnap's
account
of
mathematics
and
deductive logic is conventionalist. There is no question of justifying
deduction;
there
is
no
question
of
finding
the
correct account.
Instead
there is
only
the
engineering
task
of
examining
the
practical
conse
quences
of
adopting
this
or
that
system.
So
it is with induction.
The
traditional
question
of
justifying
induction
simply
drops
away.
One
could choose
to
have
no
inductive rules whatever. But the
pragmatic
costs
would be
high:
one
could make
no
prediction
and
this would be
followed
by
frequent
bruises and
quick
starvation. So the
question
is
not
whether
to
have inductive
rules,
but
which.
Here
again
the
matter
is
one
of
pragmatic
comparison.
If
the rules
are
too
weak,
then
we
foreclose or
complicate
useful inferences. If the rules are too
strong,
then
there
is
an
increased
chance that
one
inference will conflict with
another,
thus
requiring
constant
and
costly
revision.
The
virtues of
security
as
contrasted
with
those
of
educational
adventure
will
be
weighed differently by
different
people,
but
we
need
not
all
agree
so
long
as we
make
our
respective
choices clear. There is
no
uniquely
correct
system,
and the choice
among
the alternatives is
pragmatic.
Carnap
himself
occasionally
flirted
with
a
strategy
of
minimal risk
(Car
nap,
1936,
pp.
445-46),
that
is,
of
avoiding
any
empirical
content
for
postulates
and other
interpretative
devices,
and in
general making
the
whole
interpretive, (epistemic)
machinery
as
weak
as
possible.
He
did,
however,
recognize
that
it
is
never
possible
to
provide
absolute
guaran
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CARNAP'S
CONVENTIONALISM
155
tees
that
inconsistency
will
be
avoided,
and he
recognized
that
it is
often
more
convenient
to
adopt
a
stronger
epistemology
even
if
doing
so
is riskier.
He,
therefore,
usually
adopted
a
strategy
of
maximizing
freedom
in
laying
down
language
forms,
that
is,
epistemic
structures.
This
freedom
is still constrained
by
the
demands of
pragmatic utility,
and those constraints
are
sufficient
to
rule
out
(absolutely
or
empiri
cally)
inconsistent
systems
of belief.
It
might
be
thought
that because
I
have touched
only
on
deductive
and inductive inference
I have
omitted
all
of the
really
interesting
questions
of scientific
methodology,
such
as
the
structure
of
theories,
scientific
realism,
theoretical
concept
formation,
holism,
underdeter
mination,
etc.
This is
not
really
true.
These latter
questions
are
simply
absorbed
by
Carnap
into
a
general theory
of
scientific
inference.
For
example,
the issue of scientific realism
can
be
expressed
as
the
question
of what conclusions
to
draw from the
belief that the
observational
consequences
of
a
theory
are
true.
Shall
we,
with
the
realists,
conclude
that the
theory
is
true?
Or,
shall
we
with,
say,
van
Fraassen
conclude
something weaker? Carnap thinks that one is free to choose either
strategy,
either
principle
of inference.
Typical
realists
are
wrong
in
thinking
that there is
only
one
correct
inference. But
van
Fraassen
would
be
similarly
wrong
if
he
thought
that
a
weaker
principle
of
inference
was
the
one
uniquely
correct
principle.
So,
which choice does
Carnap
make? Does he
not
prejudice
the
case
against
scientific realism
by
emphasizing
the
conventionality
of
theoretical
concepts
and infer
ence?
The
answer
to
this
latter
question
is
no,
for
as we
shall
see
he
insists
on
the
conventionality
of observational
concepts
and
inferences
as
well.
The
two
domains of
discourse
are
thus
on a
par,
and
thus,
unsurprisingly,
Carnap
typically
adopts
the
principle
of inference that
he takes
to
be
constitutive of realism. This
discussion of realism is
only
an
example
of
the
ways
in
which various
methodological
issues
can
be
absorbed
into
a
theory
of scientific
inference,
but it is
at
least
a
highly
typical example
(Carnap,
1966,
pp.
247-56; Creath,
1985).
One
final
note
on
induction is
in
order. That
is that
Carnap's
actual
proposals
for inductive inference
get
expressed
as a
theory
of
probabil
ity.
I
cannot
even
begin
to
address the
controversies
surrounding
it,
but there is
one
feature that
will
crop
up
later.
Strictly,
probabilities
for
Carnap
are
supposed
to
be rational
betting quotients,
i.e.,
measures
of
the
degree
of confidence that is
warranted for
a
given
proposition.
Thus,
if
we
are
warranted
in
being
certain of
the truth
of
some
proposi
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156
RICHARD CREATH
tion,
then
that
proposition
has
a
probability
of
one.
If
we
should
be less than
certain,
then the
probability
should
be less than
one.
Unfortunately,
what
Carnap
actually
presents
is
not
a
theory
of
rational
degrees
of
belief
but
a
theory
of the
extent to
which
a
given
proposition
is
supported
by
the evidence.
These
are
not at
all the
same
thing,
as
is
shown
when
we
ask about the evidence itself. To
what
extent
is
the
evidence
supported
by
the evidence?
Well,
completely;
so
the
probabil
ity
of
the evidence
must
be
one.
But
Carnap
is
a
fallibilist
about
observation,
so
the
degree
of confidence
we
have
in
the evidence should
be less
than
one.
Carnap
fully
understood the
magnitude
of his diffi
culty,
but
he
never
saw a
way
around it
(Carnap,
1957).
In the
end
he
accepted
Richard
Jeffrey's suggestion
that does
not
in fact
solve
Carnap's problem.
It
may
do what
Jeffrey
needs it
to,
but
not
what
Carnap
needs
(Carnap, 1971).4
I think
Carnap
could have done
better,
and
ironically
the
way
to
do
so
is
to
develop
the
conventionalist and
pragmatist
theory
of observation
that he
already
(implicitly)
had. If
I
can
suggest
how that
can
be
done,
then
I
shall
not
only
have
helped
Carnap but enriched our understanding of observation as well.
4.
EXTENDING THE STORY TO SCIENCE: OBSERVATION
In
turning
to
observation
the
most
surprising
thing
is
how
little
Carnap
gives
us
in
the
way
of sustained discussion.
True,
there is 'On Protocol
Sentences',
produced
in
1932
just
as
his conventionalism
was
emerging
(Carnap,
[1932b]/1987).
There
he made
it
plain
that the
questions
of
what
things
were
observable
and
how
much observational
judgments
should be trusted
were
to
be answered
by
conventions.
He
also
sug
gested
some
of the
conventions he would
propose.
Even here the
discussion is
sketchy,
but
thereafter
we
get
even
less
(Carnap,
1936,
pp.
454-56).
All
told,
we are
given
many
hints,
but
no
well-worked
out
theory.
If
we
'connect the
dots',
however,
the outline of
a
general
theory
does
emerge.
Let
us
begin by laying
down
some
desiderata,
i.e.,
some
features
that
Carnap
wanted his
theory
of
observation
to
exhibit.
Some
con
ditions
will
turn out to
be
deeper
than
others,
but
that is
perfectly
acceptable.
(1)
Fallibilism:
As
previously
mentioned,
Carnap
thought
that
we
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carnap's
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157
could be mistaken
in
any
of
our
beliefs about
contingent
matters
of
fact,
including
in
our
observational
reports.
(2)
Physicalism:
While
Carnap's
physicalism
is
somewhat
broader,
here I
mean
only
that
it
should be
possible
to
observe
physical
objects
directly,
rather than
merely
to
infer their
presence,
from
beliefs about
our
mind. Let
me
emphasize
that this
physicalism
is
a
substantial
break
from both the Au?au and from Russell's brand of Cartesianism.
(3)
Objectivity:
There
are
objective
facts
about the
world,
indepen
dent of what individuals
may
think.
Thus,
observation
reports
cannot
themselves be conventions.
(4)
Non-circularity:
One
cannot
use
observation
in
order
to
show
that observation is
to
be
trusted.
Trying
to
do
so
would
presuppose
that
we
have
independent
evidence
to
judge
the truth
of the obser
vational
beliefs,
but such
independent
evidence
is
just
what
we
do
not
have. The
most
that
a
psychologist
could discover is that
her
own
observational
evidence,
however
refined,
coincides with
or
fails
to
coin
cide with
the observational
beliefs
of her
subject.
Observation will
have
its role
to
play,
but
not
this
one.
(5)
Sensitivity:
The
question
of what
things
are
observable and how
trustworthy
various observational
judgments
are
must
somehow
be
sen
sitive
to
contingent
matters
of fact. The
wholly
a
priori
accounts
of
the
Cartesian will
not
do.
Should
we
add
to
this list
a
sixth
condition,
namely,
a
condition
of
naturalism? The
answer
is
no,
but
not
because
Carnap
rejects
natural
ism.
Unfortunately,
the
word
'naturalism' has
come
to
mean
everything
to
everybody,
and
some
writers
use
it
in
various
ways
simultaneously
without
distinguishing
them. If it
means
merely
that human
beings,
their
judgments,
and the
rest
of their
mental lives
are
all
objects
and
processes
in
the natural
world and
properly
to
be studied
by
science,
then
naturalism is
just
a
weaker
version of
Carnap's
physicalism.
As
such it is
adequately
addressed
by
conditions
(2)
and
(5).
If, however,
naturalism is
meant
in
a
stronger
sense
according
to
which science
can
straightforwardly
answer
every
question,
not
only
about what is but
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158
RICHARD creath
about what
ought
to
be,
then
Carnap
rejects
this
naturalism.
This
rejection
is
expressed
in
condition
(4).
So,
how did
Carnap
propose
to
satisfy
these conditions?
His
dominant
impulse
was
to
isolate
an
observational
vocabulary.
This,
of
course,
was
a
dreadful
mistake. The distinction wanted is
at
the level
of
judg
ments,
not
words,
and
as
Carnap
fully
understood that the distinction
must
be somehow
a
matter
of
degree.
Even
so
the words used in
observational
judgments
will
get part
of
their
meaning
in
previously
described
ways,
i.e.,
via
various
postulates
and
principles
of inference.
Thus,
'red'
will
get
some
of
its
meaning
from
Nothing
is
both red
and
green
all
over
at
the
same
time construed
as a
postulate,
and from
' x is
colored'
is
directly
derivable
from 'x is
red' construed
as a
principle
of
inference.
Still,
this
is
not
enough.
We
need
rules
to
connect
judgments
involv
ing
'red'
directly
with the
world.
A
general
schema
for such
a
rule
might
be:
In
conditions
Q,
you may
assert
proposition
Pi
with
degree
of
justification
Ji.
As
a
first
approximation, perhaps
an
assertion that there is
a
red
truck
will be
assigned
a
certain
degree
of
justification, regardless
of
conditions.
Perhaps
under
the
conditions
that the
sun
is
shining
and
the
believer's
eyes
are
open,
itwould
get
a
higher degree
of
justification.
Under
the conditions that the believer has taken
a
narcotic
or
that
there is
a
billboard between the
believer and the
purported
location of
the
truck,
the
assertion would
get
a
lower
degree
of
justification,
and
so on.
Learning
a
language requires
acquiring
the
appropriate
habits. This
is
likewise
true
of
learning
the observational
parts
of
language.
If
you
have
not
learned
to
respond
to
red
objects
in
the
right
circumstances
with the
appropriate
degree
of belief
in
This
is
red ,
then
you
have
not
fully
grasped
the
meaning
of the
word
'red'.
If
you
have
not
learned
to correct
others'
observational
reports
of This
is
red
or
to
acknowledge
such
criticism
when
appropriately
made
against yourself,
then
you
have
not
fully
learned
the
meaning
of the word
'red',
either.
The
totality
of these
epistemic
rules
governing
the
use
of
the
word
'red'
or
alternatively governing
beliefs
whose
expression
uses
the word
'red' in effect defines the
word.
In
the
implicit
definition of mathema
tical
terms,
the freedom
to
lay
down
postulates
and
inference rules
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carnap's
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159
arbitrarily
was
part
and
parcel
of
our
freedom
to
define
our
terms in
whatever
way
we
desire.
So
it
is
with
terms
which have observational
uses.
Our freedom
to
construct
our
epistemology
so
that
a
non-inferen
tial belief that
something
is red is
justified
to
a
certain
degree
arises
from
our
freedom
to
define 'red'
(and 'justified')
as
we
wish.
Again,
as
in the mathematical
case,
what definitions
we
choose, i.e.,
what
precise
way
we
choose
to
fill
out
the schema
for various
conditions,
will
be
influenced
by pragmatic
considerations.
As
we
shall
see
presently,
these
pragmatic
considerations
will insure
that
the
theory
will
satisfy
the
desiderata
outlined
above.
While the
meanings
of
words
in
observational
reports
are conven
tional,
the
content
of those
reports
is
not.
That red is
a
feature
that
can
be
directly
reported
rather
than
merely
inferred is
a
fact
about
its
meaning,
and it is
a
result of
a
convention. Once
the
meaning
is
fixed,
however,
it
is
no
longer
a
matter
of choice
what
degree
of
belief
one
should
have in
a
specified
circumstance.
Thus,
this
account,
so
far,
satisfies both the
objectivity
condition and the
non-circularity
condition.
In order to see how the account might satisfy the sensitivity condition,
an
analogy
with
measurement
concepts might
be
helpful.
When
we
first
establish
a
concept
of
length
we
could choose
as
our measure
of linear
congruence
a
metal rod without
making
any
adjustments
for thermal
inhomogeneity.
Such
a
choice
might
prove
inconvenient
in
comparison
with
our
usual
'temperature
corrected'
procedures
of
measurement,
but
neither choice would
be
incorrect.
The
differences
are
only
pragmatic.
Indeed,
to
say
that
one
procedure
gave
incorrect results
presupposes
that
we
already
have
an
independent
procedure
for
determining
what
the
correct
results
are.
But
ex
hypothesi
we
do
not
yet
have such
a
procedure.
If there were a
uniquely
correct standard of measurement,
we
could
not
discover that
it
was
so even
in
principle.
Thus,
it
seems
best
to
abandon this
assumption
that there could
be such
a
uniquely
correct
standard
and
say
instead
merely
that there
are
different avail
able standards
giving
different
results
and
defining
(in
part)
different
concepts
of
length.
We
must
begin by choosing
a
standard of
measure
ment,
and
that choice
cannot
be
anything
but conventional. This should
not
suggest,
however,
that
there
can
be
no reasons
for
preferring
one
standard
over
another. We
can
discover that
some
standard is
more
convenient
to
use
overall.
The
uncorrected
rod
might
seem
to
be the
most
convenient,
but
we
have
to
consider
our
convenience
in
using
the
physics
to
be built
on
it
as
well.
If
we
wish
to
take
the
uncorrected
rod
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160
RICHARD creath
as our
standard,
then
we
are
forced
to
say
that when
the
rod
is
brought
near a
flame
the
rest
of the universe
shrinks. This is
a
perfectly
consist
ent
claim,
but such
a
physics
would be
extremely
cumbersome. Our
desire
to
avoid
a
clumsy
physics supplies
a
reason
for
preferring
a
given
standard,
but
it is
a
pragmatic
reason,
for
it
purports
to
show
at most
that
one
choice
serves our
overall
aims
and
purposes
better
than the
other choice of standard. These
pragmatic
claims
provide
the
only
sense
that
can
be made of the assertion
that
a
temperature
corrected
measuring
rod is
a
better
indicator of
length.
The
definition is
non
circular,
but
it
is also sensitive
to
contingent
matters
of fact
(Carnap,
1966,
pp.
91-95).
So
it is
with human
observation;
indeed
human
beings
can
be
thought
of
as
measuring
devices for certain features of
the world.
But
just
as
measuring
rods
can
be read
in
a
number
of different
ways,
so
can
human observers.
If
we
were
to
set
up
for
the first time
a
concept
of
color
we
could
choose
to
take
human beliefs
about
the
colors
of
objects
in
the
vicinity
as
evidence, i.e.,
take them
as
warranted
to
some
degree
even though those beliefs were not inferred from other beliefs. Alterna
tively,
just
as we
could 'correct' the
metal rod for
changes
in
tempera
ture,
so we
could
correct
the
person's
beliefs,
either
by
letting
the
beliefs
vary
in
what
degree
of
warrant
they enjoy
in
diverse
circum
stances
(e.g.,
beliefs about the colors of
objects
in
broad
daylight
are
more
justified
than
those about
objects
illuminated
by
mercury
vapor
lamps),
or
even
by taking
them
as
phenomena
providing
evidence
for
quite
different claims
(e.g.,
under these
lights
a
report
that
an
object
is
blue indicates
that it is
green,
or
more
colloquially,
under these
lights
green
things
look
blue).
The
point
is
that there
are
alternative
procedures
for
determining
what the color of an
object
is,
and it is
misleading
to
talk about the
right
procedure
apart
from
our
already
having
chosen
a
standard of
judging.
Even
so,
just
as
there
can
be
reasons
for
preferring
a
measuring
rod
corrected for
temperature
changes,
there
can
be
reasons
for
preferring
to correct
our
non-inferential
judgments
about
color for
changes
in
lighting
conditions.
And the
reasons are
still
pragmatic.
If
we
choose
'uncorrected
observers',
then either
justified
judgments
must
be
fre
quently
revised
or
else
we
must
conclude that the colors of
things
are
highly
unstable and
changes
in
color do
not
correlate
in
any
tidy
way
with
other
changes
interior
to
the
objects
themselves. There is
nothing
inconsistent about such
a
position,
but
many
will find
it
unnecessarily
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CARNAP'S
CONVENTIONALISM
161
and
undesirably
cumbersome.
In
any
case
the
argument
for
preferring
a
given
way
of
judging
color
can
show
at
most
that
one
choice
serves
our
overall
aims and
purposes
better
than another.
For
such
pragmatic
reasons
there
are
several
general
features
that
we
might
wish for in
our
rules of non-inferential
justification:
the
results
should be stable
enough
so
that the
properties
we
attribute
to
things
change
only
in
simple,
regular
ways.
The
rules should be cautious
enough
so
that
we
need
not
constantly
revise
our
most
highly
warranted
judgments.
Correspondingly,
however,
the
rules should be
strong
en
ough
to
allow useful
prediction.
Sometimes the
cost
of
making
our non
inferential
judgments
less
open
to
disconfirmation
(perhaps
by
re
stricting
them
to
claims about
our
mental
states)
is
to
make reasonable
predictions
about future
events
extremely
complex
and
difficult.
Finally,
the
rules should
permit
shared results
to
allow
for
joint
investigation
and action. For
all
these
pragmatic
reasons
Carnap
thinks that
it is
highly
prudent
to
adopt
a
language
in which
no
observational
reports
are
certain and
in
which the basic
observational
reports
are
genuinely
about public, i.e., physical objects. Carnap's physicalism represents,
therefore,
not
a
deep
insight
into the
metaphysical
nature
of the
world,
but
a
proposal
governing
what
epistemic
structures
to
set
up;
it is
a
recommendation about what is the
most
fruitful and useful
way
of
fashioning
our
epistemology.
Such
pragmatism
is the basis for
Carnap's
fallibilism
as
well.
In
this
way
conditions
(1)
and
(2)
are
satisfied,
not
by
any
possible
language
but
by
the
language
that
Carnap
recommends
on
pragmatic
grounds.
Now
we
really
can
take
probabilities
as
Carnap
wanted,
as
degrees
of rational belief. The evidence
statements
are
conventionally assigned
a
probability
(rational
degree
of
belief)
less than one. In
differing
circumstances
they
are
assigned
differing
probabilities.
From the
'out
side' these
assignment
rules
can
be viewed
as
rules of criticism.
From
the 'inside' the circumstance mentioned
in
the rules will
refer
to
items
in
the believer's
background knowledge.
Once the
evidence
is in
place
and
properly
fallible,
then
Carnap's
own
theory
of
evidential
support
will
finish
assigning probabilities
to
other
beliefs,
including
theoretical
ones.
I
have been
speaking
as
though
what
happens
in
observation
is that
a
degree
of
belief
comes
into
being
where
none
existed
before,
and
thus that
the
rules of rational belief
in
these
cases
govern
such initiation
of belief. This
may
be
a
convenient
way
of
speaking,
but it is also
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162
RICHARD CREATH
misleading.
It
would be
more
accurate to
say
that in
observation
we
adjust
previously
existing
degrees
of
belief. To
accomplish
this
the
conventional rules will have
to
contain
a
parameter
for
these
prior
probabilities
and
then
indicate how
in
varying
circumstances
these
priors
may
be
adjusted
non-inferentially.
It
may
seem
that the
enterprise
is
utterly
a
priori
and
hence
insensitive
to
contingent
facts about
our
observational
powers
and
reliability.
This
is
not
so.
As
with standards of
spatial
and
temporal measurement,
the
conventional standards
are
highly
constrained
by
pragmatic
consider
ations.
Let
us see
how
this
might
work.
We
begin
with observation
having
suitably,
albeit
conventionally,
assigned
rational
degrees
of
belief. Note that
in
using
this
word 'ration
al'
I
am
highlighting
the normative character of the
probabilities.
From
these
we
build
up
and confirm
theories
which
ultimately explain
both
the
very
processes
of observation
on
which
their
confirmation
rests
and
the
reliability
of
our
observational
judgments.
This notion of
reliability
here
is
also
a
probability
relation,
this
time understood
as a
frequency,
i.e., as a
descriptive
relation.
It
seems
fitting
that
the
degree
of
reliability
should match the
degree
of
justification
(that
is,
rational
degree
of
belief).
To
insist
that
they
must
match
moves
one
a
giant
step
further
away
from
classical
foun
dationalism
and toward
a
modest coherentism. Let
me
here
announce
Creath's
conjecture
(which
I
suspect
and
certainly
hope
is
provable,
though
I
do
not
pretend
to
have
proved
it):
if
the
degree
of
reliability
of observation
and the
degree
of its rational
credibility
do
not
match,
then
the
language
is
decision-theoretically
unstable, i.e.,
a
decision
theoretic
argument
can
be
given
from within
the
language
that
one
ought
to choose a different
language.5
If this
conjecture
is
right,
then
Carnap
needs
no
additional
requirement
beyond
the
pragmatic
con
straints
he
already
has.
Moreover,
the
system
is
highly
sensitive
to
the
contingent
facts addressed
by empirical
psychology.
If
we
concentrate
solely
on
these
explanations
of
reliability,
we
might
be
tempted
to
suppose
that
empirical
psychology by
itself
can answer
the fundamental
questions
of
epistemology.
But such
a
supposition
would be
circular,
as we
have
seen.
It would
also confuse the normative
and
descriptive
interpretations
of
probability.
Some
have
been
tempted
to
give reliability
theories of
justification
and
knowledge (Goldman,
1986).
Such
theorists,
however,
have been
hard
pressed
to
pick
out
the
relevant
conditions for
measuring reliability.
The
current
proposal
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carnap's
conventionalism
163
helps
these reliabilists
by
specifying
in
the conditions
(Q),
mentioned
in
the
epistemic
rules,
what the relevant conditions
are.
At
the
same
time that it shows what
is
right
about
reliabilism,
the
current
proposal
shows how that view
must
be
embedded
in
a
larger
context.
Carnap's philosophy
began
with
a
rejection
of
intuition
as
a source
of
knowledge.
From
the
current
vantage
point
we can now see
that
the
objections
were
pragmatic.
Intuitive
judgments
are
unreliable,
conflict
ing,
and unshared.
In
short,
no
explanation
of the
reliability
of such
a
process
was
(or
could
be)
forthcoming.
The
same can
be
said
of
any
trans-empirical
(i.e.,
metaphysical)
mode
of
knowing.
Thus,
even
em
piricism
is
a
proposal
to
be
defended
pragmatically,
and
Carnap
says
just
that
in
'Testability
and
Meaning'
(Carnap,
1937,
p.
33).
We have
come
full circle:
starting
with
a
rejection
of
intuition,
Carnap
constructed
a
vast
conventionalist
and
pragmatic epistemology.
Our
job
was
to
unearth
it and
to
extend
it
a
bit.
Carnap
could then
not
only
avoid
relying
on
intuition,
but also
(pragmatically)
justify
in
detail
his
having
done
so.
That is
no
small
accomplishment
for
Carnap's
Hilbertization of the language of science. If Feigl could have foreseen
what it would lead
to,
perhaps
he
would have smiled
right along
with
Carnap.
NOTES
1
Carnap
found
it
nearly
impossible
to
criticize
anyone
he
deeply
admired,
but
clearly
Russell
was
a
special
case.
From
very
early
in his
career
Carnap
devoured
the work
of
Russell,
and from it
he
drew the
reassurance
of
a
kindred
spirit
as
well
as
inspiration
for
his
own
work. To this Russell
responded
with
help
and
generosity; Carnap
would have
described the older
man as
a
'father
figure'.
Furthermore,
as
is well
known,
Russell
frequently changed
his mind
even on
major
issues. As
it
happens
the
book of Russell
that
most
influenced
Carnap
was
Our
Knowledge of
the External World
(George
Allen
and
Unwin,
London,
1914).
That book
was
plainly
the
inspiration
for the
Au?au
as
well
as
for
Carnap's
conviction that the task of
philosophy
was
strictly
the
logic
of science.
Indeed,
Carnap
penciled
in
at
the end of the
third
chapter
of his
personal
copy:
This
...
is
my
task
(see
copy
in the Rudolf
Carnap
Collection,
University
of
Pittsburgh,
p.
97).
But
the first
chapter
of
Russell's book is
a
vigorous
attack
on
the
very
idea that
intuition
is
a source
of
knowledge.
Thus,
Carnap
could,
not
implausibly,
believe
that
Russell had
repented
his
previous
error
and hence
no
longer
needed the criticism
that
Carnap
didn't
want
to
give
anyway.
2
Carnap usually
avoided
describing
his work
as
epistemology
for
reasons
to
be
given
presently.
But
not
always.
In
scattered
passages throughout
his
writing
he conceded its
epistemic
character.
Quine,
too,
intermittently
has
described
Carnap's
basic
notions
as
epistemological.
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164
RICHARD
CREATH
3
Perhaps
it
is
unnecessary
to
belabor
this
point
as
I have
done,
but
Burton Dreben
has
reached
a
contrary
conclusion.
He is
often
insightful
in
these
matters,
so
he
may
be
right.
In
any
case,
it
is unwise
to
disagree
with
him without clear and
cogent
reasons.
4
I
do
not
mean
to fault
Jeffrey
here. His intentions
differ
from
Carnap's,
and
the
theory
he advances
together
with
whatever
problems
it faces
likewise differ. Even
so,
Jeffrey's
suggestions
are
constructive,
and
Carnap
finds them
helpful.
If it does
not
fully
solve
Carnap's
difficulty,
that is
a
problem
for
Carnap,
not
Jeffrey.
5
As
Robert
Nozick
has
pointed
out
in
conversation,
there
is
no
guarantee
here
that
a
language
for
which
the
degree
of
reliability
of observation and the
degree
of its rational
credibility do match will be normal from our usual perspective. A sufficiently weird
original assignment might
support
a
weird
theory
which
would
explain
the odd
reliability.
In
fact, however,
all of this is
pretty
harmless. As with all
measurements,
the
results
would be relativized
to
the
procedures
of
measurement
at
hand. For
example,
one
can
measure
the universe
with
a
rubber
measuring
rod;
the results
will
be weird from
our
current
perspective;
but
because the results have
to
be relativized
to
the method of
using
a
rubber
rod,
those
results
are
not
really
in conflict with
our
usual
measurements.
This
should
also
suggest
that
even
if
degrees
of
reliability
and rational
credibility
match,
there
may
be other
pragmatic
considerations that would
make the
language
decision
theoretically
unstable. We
all
assume
that this is the
case
for the
use
of
a
rubber
measuring
rod. Doubtless
it is
also
true
with
many
weird initial conventions of observational
justifi
cation.
Finally,
there
would be
nothing
wrong
if
it should be discovered that
there
is
more
than
one
decision-theoretically
stable
language.
This is
just
what
one
would
expect
under the
assumption
that
these
are
conventions.
REFERENCES
Carnap,
Rudolf:
[1932a]/1959,
'The Elimination of
Metaphysics
Through
the
Logical
Analysis
of
Language',
in
A.
J.
Ayer
(ed.),
Logical
Positivism,
trans,
by
Arthur
Pap,
Free
Press,
New
York,
pp.
60-81.
Carnap,
Rudolf:
[1932b]/1987,
'On Protocol
Sentences',
Nous
XXI,
457-70.
Carnap,
Rudolf:
[1934J/1937,
The
Logical
Syntax
of
Language,
trans,
by
Amethe Smea
ton,
Routledge
&
Kegan
Paul,
Ltd.,
London.
Carnap,
Rudolf:
1935,
Philosophy
and
Logical Syntax, Kegan
Paul,
Trench,
Trubner
&
Co.,
London.
Carnap,
Rudolf:
1936,
'Testability
and
Meaning',
Philosophy of
Science
III,
419-71.
Carnap,
Rudolf:
1937,
'Testability
and
Meaning',
Philosophy of
Science
IV,
1-40.
Carnap,
Rudolf:
1950,
Logical
Foundations
of
Probability,
University
of
Chicago
Press,
Chicago.
Carnap,
Rudolf:
1957,
Letter
to
Richard
Jeffrey
of 17
July,
unpublished;
examined with
permission
of Professor
Jeffrey.
Carnap,
Rudolf:
1966,
Philosophical
Foundations
of
Physics,
Basic
Books,
New York.
Carnap,
Rudolf:
1971,
'Inductive
Logic
and Rational
Decisions',
in Rudolf
Carnap
and
Richard Jeffrey (eds.), Studies in Inductive Logic and Probability, Vol. 1, University
of California
Press,
Berkeley,
pp.
5-31.
Creath,
Richard:
1985,
'Carnap's
Scientific
Realism: Irenic
or
Ironic?',
in Nicholas
Re
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carnap's
conventionalism
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scher
(ed.),
The
Heritage of Logical
Positivism,
University
Press of
America,
Lanham,
MD,
pp.
117-31.
Feigl,
Herbert:
1975,
'Homage
to
Rudolf
Carnap',
in
Jaakko Hintikka
(ed.),
Rudolf
Carnap,
Logical
Empiricist,
D.
Reidel, Dordrecht,
pp.
xiii-xviii.
Frege,
Gottlob:
1980,
Philosophical
and Mathematical
Correspondence,
ed.
by
Brian
McGuinness,
trans,
by
Hans
Kaal,
University
of
Chicago
Press,
Chicago.
Goldman,
Alvin
I.:
1986,
Epistemology
and
Cognition,
Harvard
University
Press,
Cam
bridge,
MA.
Quine,
W.
V.
O.:
[1936]/1966,
'Truth
by
Convention',
in
Ways
of
Paradox and Other
Essays, Random House, New York, pp. 70-99.
Russell,
Bertrand:
[1912J/1959,
The Problems
of Philosophy,
Oxford
University
Press,
London.
Department
of
Philosophy
Arizona State
University
Tempe,
AZ
85287
U.S.A.