Oct 10, 2012

Elegi Menggapai "Mathematical Truth"

By Marsigit
Yogyakarta State University

It 1 is usually thought that mathematical truths are necessary truths. Two main views are possible i.e. either they are known by reason or they are known by inference from sensory experience.

The former rationalist view is adopted by Descartes and Leibniz who also thought that mathematical concepts are innate; while Locke and Hume agreed that mathematical truths are known by reason but they thought all mathematical concepts were derived by abstraction from experience.

Mill 2 was a complete empiricist about mathematics and held that mathematical concepts are derived from experience and also that mathematical truths are really inductive generalizations from experience.

Weir A. theorizes that one obvious problem for neo-formalism is its apparent conflict with Gödel's first incompleteness result showing that not all mathematical truths are provable, under a certain conception of provability.

Even though the neo-formalist 3 makes no synonymy claim between 'sixty eight and fifty seven equals one hundred and twenty five' and "68+57=125" is provable', this result seems to rule out any tight equivalence between truth and proof of the sort envisaged.

According to Weir A., we need a distinction between legitimate and illicit transformations, if neo-formalism is to avoid the consequence that in mathematics there is no distinction between truth and falsity.

It 4 cannot be that a string is provable if derivable in the one true logic from some consistent set of axioms or other; even if there is only one true logic it would still follow that any logically consistent sentence i.e. a mathematical truth.

The neo-formalist, as it was notified by Weir A., perceives that provability in a practice means derivable using only inference rules which are in some sense analytic and constitutive of the meaning of our logical and mathematical operators.

There are the responses to the neo-formalist, that no rule can be meaning-constitutive if it is trivial. The inconsistency and indeed triviality of 'classical' naïve set theory 5 is a product of three things: the classical operational rules, the classical structural rules and the naïve rules or axioms.

The neo-formalist 6 agrees with the strict finitist that the only objects with a title to being called mathematical which exist in reality are the presumably finite number of concrete mathematical utterances; some of these utterances, however, are used to assert that infinitely many objects- numbers, sets, strings of expressions, abstract proofs, etc.- exist.

Mathematical truth 7 is thus linked with provability in formal calculi and in such a way as to be perfectly compatible with the claim that all that exists in mind-dependent reality are concrete objects together with their physical properties.

Field H. observes that the determinacy of mathematical statements is primarily dependent on the precision we can give to the semantics of the language in which they are expressed.

If 8 we are dealing with mathematics expressed in first order logic, then the semantics of the logic itself are pretty well nailed down and if the theory under consideration concerns a unique structure up to isomorphism then we know that each closed sentence will have a definite truth value under that interpretation, and there will only be indeterminacy if there is some substantive ambiguity about what this unique intended interpretation is.

Field H. 9 , claims that even if as in the case of arithmetic, there can be no complete recursive axiomatization of the theory, which will normally be the case where there is a unique intended interpretation.

On the other hand, Oddie G. says:

While mathematical truth is the aim of inquiry, some falsehoods seem to realize this aim better than others; some truths better realize the aim than other truths and perhaps even some falsehoods realize the aim better than some truths do. The dichotomy of the class of propositions into truths and falsehoods should thus be supplemented with a more fine-grained ordering -- one which classifies propositions according to their closeness to the truth, their degree of truth-likeness or verisimilitude. The problem of truth-likeness is to give an adequate account of the concept and to explore its logical properties and its applications to epistemology and methodology. 10

Popper 11 refers to Hume’s notion that we not only that we can not verify an interesting theory, we can not even render it more probable.

There 12 is an asymmetry between verification and falsification and while no finite amount of data can verify or probability an interesting scientific theory, they can falsify the theory.

Popper 13 indicates that it is the falsifiability of a theory which makes it scientific; and it implied that the only kind of progress an inquiry can make consists in falsification of theories.

Popper states that if some false hypotheses are closer to the truth than others, if verisimilitude admits of degrees, then the history of inquiry may turn out to be one of steady progress towards the goal of truth.

It may be reasonable, on the basis of the evidence, to conjecture that our theories are indeed making such progress even though it would be unreasonable to conjecture that they are true simpliciter. 14

Again, Oddie G. convicts that the quest for theories with high probability must be quite wrong-headed, while we want inquiry to yield true propositions, in which not any old truths will do.

A tautology 15 is a truth, and as certain as anything can be, but it is never the answer to any interesting inquiry outside mathematics and logic. What we want are deep truths, truths which capture more rather than less, of the whole truth.

Even more important, there is a difference between being true and being the truth. The truth, of course, has the property of being true, but not every proposition that is true is the truth in the sense required by the aim of inquiry.

The truth of a matter at which an inquiry aims has to be the complete, true answer.

Oddie G. illustrates the following:

The world induces a partition of sentences of L into those that are true and those that are false. The set of all true sentences is thus a complete true account of the world, as far as that investigation goes and it is aptly called the Truth, T. T is the target of the investigation couched in L and it is the theory that we are seeking, and, if truthlikeness is to make sense, theories other than T, even false theories, come more or less close to capturing T. T, the Truth, is a theory only in the technical Tarskian sense, not in the ordinary everyday sense of that term. It is a set of sentences closed under the consequence relation: a consequence of some sentences in the set is also a sentence in the set. T may not be finitely axiomatisable, or even axiomatisable at all. The language involves elementary arithmetic it follows that T won't be axiomatisable; however, it is a perfectly good set of sentences all the same. 16

If a mathematical truth 17 is taken to be represented by a unique model, or complete possible world, then we end up with results very close to Popper's truth content account.

In particular, false propositions are closer to the truth the stronger they are; however, if we take the structuralist approach then we will take the relevant states of affairs to be “small” states of affairs viz. chunks of the world rather than the entire world and then the possibility of more fine-grained distinctions between theories opens up.

Further, Oddie G. (2001) claims that a theory can be false in very many different ways; the degree of verisimilitude of a true theory may also vary according to where the truth lies.

One does not necessarily make a step toward the truth by reducing the content of a false proposition.

Nor does one necessarily make a step toward the truth by increasing the content of a false theory.

Philosophy of Mathematics, Retrieved 2004
2 Ibid
3 Weir A., 2004, “A Neo-Formalist Approach to Mathematical Truth”, Retrieved 2004
4 Ibid.
5 Ibid.
6 Ibid.
7 Ibid.
8 Field, H., 1999, “Which Undecidable Mathematical Sentences Have Determinate Truth Values?”, RJB, Retrieved 2004
9 Ibid.
10 Oddie, G., 2001, “Truthlikeness”, Stanford Encyclopedia of Philosophy, Paideia, Philosophy of Mathematics. Retrieved 2004
11Popper in Oddie, G., 2001, “Truthlikeness”, Stanford Encyclopedia of Philosophy, Paideia, Philosophy of Mathematics. Retrieved 2004
12Oddie, G., 2001, “Truthlikeness”,, Stanford Encyclopedia of Philosophy, Paideia, Philosophy of Mathematics. Retrieved 2004
13Popper in Oddie, G., 2001, “Truthlikeness”, Stanford Encyclopedia of Philosophy, Paideia, Philosophy of Mathematics. Retrieved 2004
15Oddie, G., 2001, “Truthlikeness”, Stanford Encyclopedia of Philosophy, Paideia, Philosophy of Mathematics. Retrieved 2004

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