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How is
"Exactness" Possible?
by Ferdinand Canning Scott
Schiller
It is amazing what a spell the ideal of
exactness has cast upon the philosophic mind. For
hundreds, nay thousands, of years philosophers seem
to have been yearning for exactness, and hoping
that, if only could attain it, all their troubles
would be over. All the pitfalls in the way of
philosophic progress would be circumvented, and
every philosophic science, from psychology and
logic to the remotest heights of metaphysics, would
become accessible to the meanest understanding.
Yet what a gap there is between these
professions and the practice of philosophers!
Despite of their zeal for exactness, what body of
learned men is more careless in their terminology
and more contemptuous of all the devices which seem
conducive to exactness?
Experience shows that it is quite impossible to
pin any philosophic term down to any single
meaning, even for a little while, or even to keep
its meaning stable enough to avoid gross
misunderstanding. Even the most express and solemn
definitions are set at naught by the very writers
who propounded them. The most famed philosophers
are the very ones who have been the worst
offenders. For example, Kant's fame rests in no
small measure on the tricks he played with words
like "a priori," "category," "object," and
his systematic confusion of "transcendental" and
"transcendent." There is hardly a philosophy which
does not juggle thus with ambiguous terms. If the
theories of philosophers may be interpreted in the
light of their practice, they should be the last
persons in the world to laud "exactness."
On the other hand, they might fairly be expected
to inform us what "exactness" means, or at least
what they wish it to mean. I do not find, however,
that they are at all eager to do this. Apparently
they are content to refer to mathematics as an
"exact" science, and to admonish philosophy to
respect and aspire to the mathematical ideal.
To understand exactness, therefore, we must go
to mathematics and inquire whether and in what
senses mathematics are "exact." Now it is clear
that mathematics are not exact in the sense that
mathematical objects exactly reproduce physical
realities; nor do physical realities exactly
exemplify mathematical ideals. There are no
straight lines nor circles to be found in nature,
while all the physical constants, like the year,
month, and day, are inexact. Plato knew this, but
yet thought God as a mathematician; he should have
added that if God geometrizes, He does so very
inexactly.
Hence, if the relation between realities and
mathematical ideals is conceived as a
copying or reproduction, it cannot
possibly be "exact." Which is the archetype, and
which the copy, does not matter; alike whether the
real copies the mathematical ideal, or the latter
is moulded upon the former, no exactness can be
found.
There is, however, a sense in which exactness
depends on definition; and mathematicians take
great pride in the exactness of their definitions.
A definition can be exact, because it is a
command addressed to nature, and it sounds
quite uncompromising. If the real will not come up
to the definition, so much the worse for the real!
In so far therefore as exactness depends on
definitions, mathematics can be exact. It can be as
exact as anything defined exactly.
But there appear to be limits to the exactness
thus attainable. The exactness of a definition is
limited by two difficulties. (a) In the first place
things must be found to which the definition, when
made, does actually apply. And secondly, (b) the
definition has to be maintained against the growth
of knowledge. Both these difficulties may easily
prove fatal to exactness.
As to (a), it is clear that we cannot
arbitrarily "define" the creatures of our fancy,
without limits. Definitions which apply to nothing
have no real meaning. The only sure way, therefore,
of securing that a definition will be operative and
will have application to the real, is to allow the
real, idealized if necessary, to suggest the
definition to the mathematician. The mathematician
was sensible enough to adopt this procedure. He
allowed a ray of sunlight to suggest the definition
of a straight line, and this assured to Euclidean
geometry a profitable field of application.
But it did not render the definition
immutable, and immune to the growth of knowledge.
The mathematical definition remains dependent on
the behavior of the real. If, therefore, rays of
light are found to curve in a gravitational field,
a far-reaching doubt is cast on the use of
Euclidean geometry for cosmic calculations.
As to (b), the definer retains the right to
revise his definitions. So the very framing of his
definition may suggest to the mathematician the
idea of developing it in some promising and
interesting direction. But this procedure may
entail a further definition, or redefinition, which
destroys the exactness of the first formula. Thus
when he has accomplished the "exact" definition of
a circle and an ellipse, it may occur to a
mathematician that after all a circle may be taken
as a special case of an ellipse, and that it would
be interesting to see what happens if he followed
out this line of thought. He does so, and arrives
at "the points at infinity," with their paradoxical
properties. Again the development of non-Euclidean
geometries has rendered ambiguous and inexact the
Euclidean concepts, e.g., of "triangle." Even so
elementary and apparently stable a conception as
that of the unit of common arithmetic undergoes
subtle transformations of meaning as others beyond
the original operation of addition are
admitted.
In mathematics then, as in the other sciences,
it is inevitable that the conceptions used should
grow. It is impossible to prohibit their
growth, and to restrict them to the definitions as
they were conceived at first. Indeed the process of
stretching old definitions so as to permit of new
operations is even particularly evident in
mathematics.
The method by which it is justified is that of
analogy. If an analogy can be found which
promises to bridge a gap between one notion and
another, their identity is experimentally assumed.
And if the experiment works for the purposes of
those who made it, the differences between them are
slurred over and ignored. If it were not possible
to take the infinitesimal, now as something, now as
nothing, what would be left of the logic of the
calculus? But the logician at least should remind
himself that analogy is not an exact and valid form
of argument.
Can exactness be said to inhere in the symbols
used by mathematicians? Hardly. + and -, and even
=, have many uses, and therefore senses, even in
the exactest mathematics.
The truth is that mathematical definitions
cannot be more exact than our knowledge of the
realities to which, sooner or later, directly or
indirectly, they refer. Nor can mathematical
symbols be more exact than words. It is
sheer delusion to think otherwise.
And what about words? Whence do they get their
meanings, and how are they stabilized and
modified?
Words get their meaning by being used
successfully by those who have meanings to convey.
Verbal meaning, therefore, is derivative
from personal meaning. Once a verbal meaning
is established and can be presumed to be familiar,
personal meaning can employ a word for the purpose
of transmitting a new meaning judged appropriate to
a situation in which a transfer of meaning to
others is judged necessary or desirable. Thus a
transfer of meaning is always experimental, and
generally problematic and inexact.
Moreover the situation which calls for it is
always more or less new. Hence a successful
transfer, that is the understanding of a meaning,
always involves an extension of an old
meaning; and in the course of time this may result
in a complete reversal of the initial definition.
For example, when the "atom" was first imported
into physics, it was defined as the ultimate and
indivisible particle of matter. Now, notoriously,
it has been subdivided so often that there seems to
be room in it for an unending multitude of parts;
and its exploration is the most progressive part of
physics. The word remains, but its definition has
been radically changed. For the scientist always
has an option when he finds that his old words are
no longer adequate: he can either change his terms,
or else his definitions. But there is, and can be,
no fixity and no exactness about either.
There is a further difficulty about definitions.
All words cannot be defined. Wherever the definer
begins, or ends, he makes use of terms not yet
defined, or has recourse to definitions revolving
in a circle. So, if he hankers after exactness, he
declares that some terms are indefinable and need
no definition. This subterfuge is utterly unworthy
of an exact logician. For if he holds that these
indefinables are yet intuitively understood or
apprehended, he enslaves his "logic" to psychology.
If he admits that he cannot guarantee that any two
reasoners will understand the indefinables alike,
he explodes the basis of all exactness. Thus even
the exactest definitions are left to float in a sea
of inexactitude.
The situation grows still more desperate if the
logician realizes that, to achieve exactness, he
must eradicate and overcome the potential ambiguity
of words. He must devise words which exactly fit
the particular situation in which the words are
used. For otherwise the same word will be permitted
to mean one thing in one context, another in
another. It will be what logicians have been wont
to call "ambiguous." In this, however, they may
have been mistaking for a flaw the most convenient
property of words, namely their plasticity and
capacity for repeated use as vehicles of
many meanings.
For the alternative of demanding a one-one
correspondence between words and meanings, seems
incomparably worse. I remember this was tried once
by Earl Bertrand Russell, in a sportive mood. It
was not long after the war, and he had just emerged
from the dungeon to which he had been consigned for
an ill-timed jest, that he came to Oxford to read a
paper to a society of undergraduate philosophers,
on what he called "vagueness." I was requested to
"open the discussion" on this paper, and so
obtained what in Hollywood is called a "preview" of
it. What was my amazement when I found that
Russell's cure for "vagueness," that is, the
applicability of the same word to different
situations, was that there should be distinctive
words for every situation! Certainly that would be
a radical cure; but in what a state would it leave
language! A language freed from "vagueness" would
be composed entirely of nonce words, "hapax
legomena," and almost wholly unintelligible. When I
pointed out this consequence, Russell cheerfully
accepted it, and I retired from the fray.
Russell had rightly diagnosed what was the
condition of exactness. But he had ignored the fact
that his cure was impracticable, and far worse than
the alleged disease. Nor had he considered the
alternative, the inference that therefore
the capacity of words to convey a multitude of
meanings must not be regarded as a flaw, but that a
distinction must be made between plurality of
meanings and actual ambiguity.
It is vital to logic that the part words play in
transmitting meaning from one person to another
should be rightly understood; but does not such
understanding reduce the demand for "exactness" to
a false ideal?
What finally is the bearing of these results on
the pretensions of logistics?
It seems to reduce itself to a game with
fictions and verbal meanings. (1) It is clear that
it is a fiction that meanings can be fixed, and
embodied in unvarying symbols. (2) It is clear that
the verbal meanings to be fixed are never the
personal meanings to be conveyed in actual knowing.
The assumption that they can be identified is just
a fiction too. (3) There appears to be no point of
contact between the conventions of this game and
the real problems of scientific knowing. This is
the essential difference between logistics and
mathematics. Pure mathematics is a game too, but it
has application to reality. But logistics seems to
be a game more remote from science than chess is
from strategy. For in a science the meanings
concerned are those of the investigators, that is,
are personal. They are also experimental.
They respond to every advance in knowledge, and are
modified accordingly. Their fixity would mean
stagnation, and the death of science. Words need
only enough stability of meaning, when they are
used, for the old senses (which determine their
selection) to yield a sufficient clue to the new
senses to be conveyed, to render the latter
intelligible. In their context, not in the
abstract. In the abstract they may remain
infinitely "ambiguous," that is, potentially
useful. This does no harm, so long as it does
not mislead in actual use. And when an experimenter
ventures on too audacious innovations upon the
conventional meanings of his words, the right
rebuke to him is not "You contradict the meaning of
the words you use," but "I do not understand; what
do you mean?"
I am driven then to the conclusion that
logistics is an intellectual game. It is a game of
make-believe, which mathematically trained pedants
love to play, but which does not on this account
become incumbent on every one. It may have the
advantage that it keeps logisticians out of other
mischief. But I fail to see that it has either any
serious significance for understanding scientific
knowing or any educational importance for
sharpening wits!
Excerpted from Acts of the
Eighth International Congress of Philosophy,
1934
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