Quine on PropositionsPart-III:Diffuseness of Empirical Meaning

November 16, 2014

Evidence and Theory

Suppose an experiment has yielded a result contrary to atheory currently held in some natural science.

The theory comprises a whole bundle of conjointhypotheses, or is resoluble into such a bundle.

The most that the experiment shows is that at least oneof those hypotheses is false; it does not show which.

It is only the theory as a whole, and not any one of thehypotheses, that admits of evidence or counter-evidencein observation and experiment.

Contarary Evidence: Evidence Against a Theory,

Not Sentences

And How Wide is a Theory? No part of science is quiteisolated from the rest.

Parts as disparate as you please may be expected to sharelaws of logic and arithmetic, anyway, and to share variouscommon-sense generalities about bodies in motion.

Legalistically, one could claim that evidence counts alwaysfor or against the total system, however loose-knit, ofscience.

Evidence against the system is not evidence against anyone sentence rather than another, but can be acted onrather by any of various adjustments.

An Important Exception

An important exception suggests itself: surely anobservation is evidence for the sentence that reports thatvery observation, and against the sentence that predictedthe contrary.

Our legalist can stand his ground even here. He cantpoint out that in an extreme case, where beliefs that havebeen supported overwhelmingly from time immemorial aresuddenly challenged by a single contrary observation, theobservation will be dismissed as illusion.

Observation Sentences and Theretical Sentences.

What is more important, however, is that usuallyobservation sentences are indeed individually responsiveto observation. This is what distinguishes observationsentences from theoretical sentences.

It is only through the responsiveness of observationsentences individually to observation, and through theconnections in turn of theoretical sentences toobservation sentences, that a scientific theory admits ofevidence at all.

Why certain sentences are thus individually responsive toobservations becomes evident when we think about howwe learn language

Ostensive Learning of Linguistic Expressions

Many expressions, including most of our earliest, arelearned ostensively.

They are learned in the situation that they describe, or inthe presence of the things that they describe.

They are conditioned, in short, to observations; and topublicly shared observations, since both teacher andlearner have to see the appropriateness of the occasion.

Learning And Behavioural Criteria of Observation

Sentences

Now if an expression is learned in this way by everyone,everyone will tend uniformly to apply it in the presence ofthe same stimulations.

This uniformity affords, indeed, a behavioral criterion ofwhat to count as an observation sentence.

It is because of this uniformity, also, that scientists whoare checking one anothers evidence gravitate toobservation sentences as a point where concurrence isassured.

Connections Between Observation Sentences and

Non-observaton Sentences

We learn further expressions contextually in ways thatgenerate a fabric of sentences, complexly interconnected.

The connections are such as to incline us to affirm ordeny some of these sentences when inclined to affirm ordeny others.

These are the connections through which a theory ofnature imbibes its empirical substance from theobservation sentences.

They are also the connections whereby, in an extremity,our theory of nature may tempt us to ignore or disavowan observation, though it would be regrettable to yieldoften to this temptation.

Theory Under-determined by Our Data

The hopelessness of distributing empirical informationgenerally over separate sentences, or even over fairly largebundles of sentences, is in some sense widely recognised,if only by implication.

It will be widely agreed that our theory of nature isunder-determined by our data.

It is under-determined not only by the observations weactually have made and will make, but even by all theunobserved events that are of an observable kind.

Briefly, our theory of nature is under-determined by allpossible observations.

What Does Under-determination of a Theory by

All Possible Observations Mean?

This means that there can be a set H of hypotheses, andan alternative set H incompatible with H.

And it can happen that when our total theory T ischanged to the extent of putting H for H in it, theresulting theory T still fits all possible observations justas well as T did.

Evidently then H and H convey the same empiricalinformation, as far as empirical information can beapportioned to H and H at all;but still they areincompatible.

Why Notion of Propositions as Empirical Meanings

Stubborn?

This reflection should scotch any general notion ofpropositions as empirical meanings of sentences. Whythen is the notion so stubborn?

Partly because the separate sentences of science andcommon sense do in practice seem after all to carry theirseparate empirical meanings.

This is misleading, and explicable.

Explication of the Misleading Seperateness I

Thus suppose that from a combined dozen of ourtheoretical beliefs a scientist derives a prediction inmolecular biology, and the prediction fails.

He is apt to scrutinise for possible revision only the halfdozen beliefs that belonged to molecular biology.

He would not amper with the more general half dozenhaving to do with logic and arithmetic and the grossbehavior of bodies.

This is a reasonable strategy a maxim of minimummutilation.

But an effect of it is that the portion of theory to whichthe discovered failure of prediction is relevant seemsnarrower than it otherwise might.

Explication of the Misleading Seperateness II

Probably, moreover, he will not even confront the sixbeliefs from molecular biology impartially with the failureof prediction;

he will concentrate on one of the six, which was moresuspect than the rest.

Scientists are indeed forever devising experiments for theexpress purpose of testing single hypotheses;

and this is reasonable, insofar as one hypothesis has beenfixed upon as more tentative and suspect than other partsof the theory.

Rejection of Hypthesis is not That of Single

Sentence

It would be a mistake, however, to see the scientistsmove as one of questioning a single hypothesis whilekeeping all else fixed.

His experiment is prompted by suspicion of onehypothesis, yes;

and if the test proves negative he is resolved to rejectthat hypothesis, but not quite it alone.

Along with it he will reject also any which, as he says,imply it.

Quine thinks that he must not lean on a notion ofimplication, for he is challenging that (or the associatednotion of equivalence, which is simply mutualimplication).

Rejection of a Group of Sentences Because of their

Interconnections

But we do have to recognise that sentences areinterconnected by means of associations entrenched inbehavior.

There are the complex interconnections lately remarkedupon: connections of varying strengths that incline us toaffirm or deny some sentences when affirming or denyingothers.

Whoever rejects one hypothesis will be led by these habitpatterns to reject other sentences with it.

Allocation of Seperate Evidence to Observation

Sentences Alone

The scientists strategy of dividing and conquering servesscience well, but it does not show how to allocateseparate empirical evidence to separate sentences.

We can allocate separate evidence to each observationsentence, but that is about the end of it.