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Home , Description, Logical positivism, Reference, Sense data, Truth

Chapter

Logical

Iwant neither that pluto cracy grasping and mean nor that

demo cracy go o dy and medio cre o ccupied solely in turning the

cheek where would dwell sages without curiosity who

shunning excess would not die of disease but would surely die

of ennui

Poincare quoted in Runes ToP p

Science itself therefore may b e regarded as a minimal problem

consisting of the completest p ossible presentment of with

the least possible expenditure of

Mach Newman WMVol p

Historical Background

In this chapter wewilllookat the most inuential

of in the twentieth century In spite of the

that logical p ositivism has b een abandoned by most of

science its inuence continues in many disciplines including physics

and We b e esp ecially concerned with logical

p ositivisms view of which is roughly the only real

CHAPTER LOGICAL POSITIVISM

knowledge is scientic knowledge by a pro cess of logical analysis

scientic knowledge can b e reduced to symb olic formulas constructed

from atomic facts Certainly assertion is nothing new So crates

said as much when he distinguished scientic knowledge

from a practice empeiria see Section Furthermore assertion

is implicit in Pythagorianism and is a continuous theme in most

Western from and through Hobb es and

Leibnitz to Bo ole and Hilb ert In this logical p ositivism is just

the of this long tradition

The ma jor innovation of logical p ositivism follows from a new under

standing of scientic knowledge and in the resulting view of the atomic

constituents of knowledge Throughout most of these years sci

entic knowledge was viewed rationalisticallyanditwas assumed that

the atomic constituents were some kind of selfevident involving

basic categories that required no denition However b eginning in the

Renaissance there was a growing recognition of the of observa

tion and exp eriment activeintervention in and a corresp onding

increase in scepticism ab out the self of any prop osition In

deed if empiricist philosophers were willing to grant selfevidence to

anything it was to sense rather than to the metaphysical prop o

sitions favored by the rationalists In the past the of knowledge

had b een Euclidean geometry but the new to ok physics as

its ideal

Although logical p ositivism originated in Germany in the s

a many of its ro ots are AngloAmerican First there is empiricism

strong theme in British philosophybacktoDavid Hume

Thomas Hobb es and Francis Bacon Second

there is American originated byCSPeirce

William James and with its em

phasis on the observable consequences of actions Finally there was

logical analysis strongly represented in the Continental idealist tradi

tion but turned into a technical to ol by the British philosophers G E

Mo ore and

Logical p ositivism combined these AngloAmerican developments

with the existing p ositivist tradition on the Continent which originated

with the French He argued

that each branchofhuman went through three stages

HISTORICAL BACKGROUND

in the theological stage are based on the volition of go ds

in the metaphysical stage explanations are based on abstract forces in

the positive or scientic stage phenomena are not explained at all

but are simply connected bylaws Comte says

FinallyinthePositive state the human recogniz

ing the imp ossibility of obtaining gives up

the search after the origin and destination of the

and a knowledge of the nal causes of phenomena It only

endeavors nowtodiscover bya wellcombined use of rea

soning and the actual of phenomena

that is to say their invariable of succession and

likeness quoted in Runes ToPp

The famous French mathematician and philosopher Jules Henri

Poincare applied p ositivist to physics and was con

cerned with the construction of basic physical out of our sen

sations and p erceptions In this way he prepared the way for Einsteins

reconstruction of space and gravity in his sp ecial and general

relativity see p

The Austrian physicist to ok a very sim

ilar view and argued that the laws of physics as of all the

are just shorthand summaries of relationships b etween the observers

exp eriences

y It is the ob ject of science to replace or save exp eriences b

the repro duction and anticipation of facts in thought

This economical oce of science which lls its whole life

is apparent at rst glance and with its full recognition all

in science disapp ears

Every scientic and mass energy atoms must b e

reduced to relations b etween observable quantities These in turn

are relationships among

Prop erly sp eaking the is not comp osed of things as

its elements but of colors tones pressures spaces

in short what we ordinarily call individual sensations

A relevant selection from Machs ScienceofMechanics from whichthese

quotations are taken is reprinted in Newman WMVol pp

CHAPTER LOGICAL POSITIVISM

This view led Mach to detailed investigations of sensation and p ercep

tion for example in his Space and Geometry he carefully distin

guishes the space of physics from the physiological space up on which

its based and in the latter category he analyzes the space of vision and

the space of touch which of course are not the same These analyses

formed a starting p oint for Einsteins relativitywork p

Muchlike Comte Machsaw science as an advance over

Where neither conrmation nor refutation is p ossible science is not

concerned He rejected anything not reducible to exp erience as not

true knowledge a characteristic attitude of p ositivism and by

reducing statements to exp erience he hop ed to exp ose sig

nicance of the and get rid of metaphysical obscurities As

Hume said long b efore

If we take in our hand anyvolume of divinityorscho ol

metaphysics for instance let us ask Does is contain any ab

stract reasoning concerning quantity or number No Does

it contain any experimental reasoning concerning matter

of fact and No Commit it then to the ames

for it can contain nothing but sophistry and illusion Enq

Conc Human Underst sec pt

In Mach b ecame a professor of physics at the University of Vi

enna and with him we come to the do orstep of the the

fountainhead of the logical p ositivist movement However b efore we

discuss it wemust consider imp ortantcontributions from the analytic

tradition up on which the logical p ositivists also dep ended

Logical

Russell Knowledge by Acquaintance and

Description

In many resp ects logical p ositivism was motivated by the same desires

for p erfect clarity and absolute certaintythathave driven muchofthe

of epistemology from the time of Pythagoras The particular

form that this quest has taken in the analytic traditionwhich has

dominated Anglo in the twentieth century and

which includes logical p ositivism is the b elief that analysis can b e

pursued down to certain indivisible elements which are in some way

incorrigible and hence justify the edice constructed from

them

One form of this is the of logical atomism develop ed by



Bertrand Russell in the rst decades of the twentieth century

He distinguished know ledge by acquaintancewhich is indubitable from

know ledge by whichmay b e in error Examples of knowl

edge by acquaintance are sense data and the contents of our own mem

ory So for example if I were p erceiving a patchofyellow color in

a certain place in my visual eld Russell would take that fact to b e

unassailable though I could certainly b e incorrect in assuming that

Im seeing a yellow ob ject since it could b e a hallucination I might

have jaundice or b e wearing yellow sunglasses etc etc Similarly

my memory that a certain p erson attended my fth birthdayparty

might b e mistaken but I cannot b e mistaken in the fact of having that

recollection

A common logical is the use of to which nothing

answers The classic example is the presentKingofFrance since

France do es not have a king Therefore when I make an assertion

such as the presentKingofFrance is bald it is neither true nor

since it is not an assertion ab out anything Suchknowledge by

description is fallible since it contains descriptions that mayfailin



their that is they do not refer to anything In an

ob ject of acquaintance acts likea logical ly proper and cannot fail

in its reference by of my p erceiving it the sp ot of yellowIm



The logical atomism of Russell diers from that of Leibnitz p in that the

former is empirical whereas the latter is rationalistic though interestingly b oth

to ok the self to b e an elementary given Sources for this section include Russell

LA and Russell PLA



The pitfalls of reference are illustrated by the fo otnoted for had I said

they refer to nothing it mighthave implied that there is a thing Nothing to

which descriptions refer when nothing else answers the description We could then

make a career out of investigating the prop erties of this Nothing Indeed Alexis

Meinong did precisely that since he gave a kind of logical realitytoany

intentional that is any ob ject of Consideration of Meinongs

work led Russell to his

CHAPTER LOGICAL POSITIVISM

p erceiving refers to itself For example I may b e incorrect in thinking

that I am seeing a dog I may b e hallucinating etc etc but I cannot

b e incorrect in my b elief that Im seeing a certain spatial arrangement

of patches of color and texture canoid color patches as Russell calls

them whichIhave come to asso ciate with dogs

The way to then in the grounding of all descriptions

in ob jects of acquaintance In the same way that he dened numb ers in

terms of more basic logical concepts the usual ob jects of science would



b e dened in terms of sense data For example a canoid p erception

might b e dened as an extremely complex logical construction of el

ementary prop ositions referring to canoid color patches In this way

we might b e absolutely certain ab out whether we are having a canoid

p erception though wemight b e mistaken ab out seeing a dog Rus

sell was convinced that every meaningful prop osition could b e analyzed

into a description involving ob jects of acquaintance in his

Thus in every prop osition that we can apprehend ie not

only in those whose truth or falseho o d we can judge of

but in all that we can think ab out all the constituents are

really entities with whichwehave immediate acquaintance

Russell OD p

Wittgenstein The Tractatus

The limits of my mean the limits of myworld

Wittgenstein TLP

ebeen We feel that even when al l possible scientic questions hav

answered the problems of life remain completely untouched Of

course there are then no questions left and this itself is the

answer



Or whatever the elementary terms might b e Russell changed his mind more

the once in his long career The nature of the atomic facts was also a p erennial

problem for the logical p ositivists I may add in passing that the whole that

sense data such as canoid color patches are p erceptually simple is op en to

criticism and is in fact rejected by the theories advo cated in the second half of this b o ok

LOGICAL ATOMISM

Wittgenstein TLP

Wovon man nicht sprechen kann darub er muss man schweigen

Whereof one cannot sp eak thereon one must remain silent

Wittgenstein TLP

It is rare enough when someone revolutionizes philosophyintheir

own lifetime has the distinction of

having accomplished it twice Indeed his views changed so completely

that it is common to treat early Wittgenstein and late Wittgenstein

almost liketwo dierent philosophers In this chapter the topic is early

Wittgenstein late Wittgenstein will b e considered in Section

Wittgensteins career was anything but ordinary Educated as an

engineer he b ecame interested in and and studied

under Russell at Cambridge He retreated to a primitive home in Nor

way to think ab out philosophy and during the First World War he

completed the Tractatus which is the sub ject of this section Then

he retired from philosophy since he thought he had solved its prin

cipal problems and held various jobs including village scho olmaster

and gardener in a monasteryHowever he b egan to question his con

clusions and eventually rejected most of them Therefore in he

returned to Cambridge University and philosophyHowever He b e

lieved that b eing a professor jeopardized the intellectual integrityofa

philosopher Hartnack WMP p so in he retired to a cabin

bridge in when on the west coast of Ireland He returned to Cam

he was diagnosed with cancer and died in Although he published

only the Tractatus after his death his students edited and published



his manuscripts and the notes he had dictated to his classes

Wittgensteins only published work the Tractatus LogicoPhilosophicus

Wittgenstein TLP had great inuence on Russell after World War

I and was seminal to the logical p ositivist movement Its style is terse

and dogmatic for example it b egins Wittgenstein TLPp



HartnackWMP is a go o d brief intro duction to Wittgensteins thought b oth early and late

CHAPTER LOGICAL POSITIVISM

The world is all that is the case

The world is the totality of facts not of things

The world is determined by the facts and by their b eing al l the

facts

For the totality of facts determines what is the case and also

whatever is not the case

The facts in logical space are the world

The world divides into facts

Wittgensteins own onesentence summary of the Tractatus is the oft

quoted

What can b e said at all can b e said clearly and what we

cannot talk ab out wemust pass over in silence

Was sichub erhaupt sagen lasst lasst sich klar sagen und

wovon man nicht reden kann darub er muss man schweigen

Wittgenstein TLPp

Wittgenstein b elieved that many philosophical problems are a result of

misunderstanding language and the wayitworks an opinion he did not

reject later Language is only capable of expressing certain ideas and

for these we should use a language ideally suited to accuracy of expres

sion Those things ab out whichwecannotspeakwhich Wittgenstein

called the mystical das Mystische must b e passed over in silence

b ecause it is a philosophical error to try to express the inexpressible

He classed ethics and in the mystical However Wittgen

steins insistence on the existence of imp ortant inexpressible problems

was ignored by the logical p ositivists

The greater part of the Tractatus is devoted to the expressible and

o imp ortant theses The atom its clear expression which is based on tw

istic thesis says that analysis terminates in elementary facts though

Wittgensteins version of this thesis is not the same as Russells or the

logical p ositivists I will pass over the details The picturing thesis

THE VIENNA CIRCLE AND VERIFIABILITY

which is based on the work of Frege and Russell says that language

when correctly analyzed is seen to b e isomorphic to the world

We picture facts to ourselves

A picture presents a situation in logical space the existence and

nonexistence of states of aairs

A picture is a mo del of

If a fact is to b e a picture it must have something in common

with what it depicts

Russell in his intro duction to the Tractatus explains the picturing

thesis as follows

In order that a certain sentence should assert a certain fact

there must however the language may b e constructed b e

something in common b etween the structure of the sentence

and the structure of the fact Wittgenstein TLPpx

Thus the structure of the world maybediscovered by analyzing the

p ossible logical structure of language that depicts that is language

that do es not attempt to express the inexpressible

The Vienna Circle and Veriability

Background

Logical p ositivism was b orn in the s with the formation of the

Vienna Circle a group of physicists mathematicians and so cial scien

tists who met every week in Vienna under



a philosopher at the The philosophical move

ment that they started was later known as logical positivism logical

scientic empiricism In part b ecause of the ightof empiricism and



Among the memb ers of the Vienna Circle were

FriedrichWaismann Kurt Godel Phillip Frank Karl Menger Hans Hahn and A

J Ayer

CHAPTER LOGICAL POSITIVISM

philosophers and scientists from Nazi Germany logical p ositivism b e

came the dominant in the AngloAmerican world

often more implicitly than explicitly

Although there were disagreements from the b eginning in logical

p ositivism and they multipliedasthemovement progressed there are

several themes that are characteristic First it is empirical in its re

quirement that all knowledge except for the analytic of math

ematics and logic cf p b e derived from exp erience It is positivist

in its rejection of metaphysical claims that cannot b e veried by ap

p eal to the givens literally the data of exp erience Its scientic in

holding that the metho ds of the sciences esp ecially physics are

the only waytotrueknowledge Finally its logical in recognizing

the imp ortant role that logical constructions play in relating basic data

sensations measurements etc to the higher order ob jects of scientic

theories atoms waves energy etc In this way the p ositivists tried to

augment Machs empiricism with the more mathematical approachof

Poincare Weve seen that Russell and Wittgenstein advo cated a sim

ilar viewp oint so its hardly surprising that the Tractatus was treated

almost as sacred scripture and was read out loud at Vienna Circle



meetings

Veriability and

One of the cen tral tenets of logical p ositivism was the veriability prin

ciplewhichsays that the meaning of a prop osition lies in its mo de of

verication In other words its meaning consists in the measurements

wewould havetomake to decide whether it is true or false As Schlick

PR p said

The criterion of the truth or falsity of the prop osition then

lies in the fact that under denite conditions given in the

denition certain data are present or not present If this

is determined then everything asserted by the prop osition

is determined and I know its meaning



For a time the prophet attended the meetings in p erson but in the end he was

less welcome than his revelations

THE VIENNA CIRCLE AND VERIFIABILITY

For example consider the prop osition that the temp erature of a

certain volume of water is C What do es it mean The logical p osi

tivist answer is that if you put a thermometer into the water and read

it then it will show C However reading a thermometer is still a

rather vague description so it is more precise to saythatwe place a

Celsius thermometer in the water wait for its reading to stabilize and

then observe that its opp osite the mark This is still somewhat

far from sense data however so a further explication might b e When

the meniscus of the mercury column stops moving it is closer to line

marked than to the lines marked or In general the

is that all meaningful factual statements can b e reduced to measure

ments and measurements are ultimately simple p erceptual

such as determining which mark on a dial is the closest to a p ointer

A corollary of this reduction of meaning to verication conditions is

the conclusion that any prop osition that cannot b e veried by app eal

to data is literal ly meaninglessInSchlicks words PR p

A prop osition which is such that the world remains the same

whether it b e true or false simply says nothing ab out the

world it is empty and communicates nothing I can giveit

no meaning

Since traditionally metaphysics is the study of the basic grounds of ex

istence whichistaken to b e prior to empirical verication its fails the

veriability test and among the p ositivists metaphysics b ecame a

of derision for meaningless mumb ojumb o In this waytheysaw

ay all the unan the veriability as a razor that would cut aw

swerable b ecause meaningless questions that had vexed philoso

phers for ages such as the existence of the external world It would

not solve metaphysical problems it would dissolve them

For a sp ecic example in the early days of atomic theory when the

existence of atoms was inferred from chemical laws there were vigorous

debates ab out the reality of atoms Were there really indivisible bits



of matter or were they simply a convenient ction for calculation

Though many of the senior scientists at the time were against the reality



In more recent times there have b een similar debates ab out the reality of quarks

CHAPTER LOGICAL POSITIVISM

of atoms the tide eventually turned against them and mo dern imaging

techniques make it nearly imp ossible to their existence The

p ositivist answer would b e Tell me what you mean by existence

by reducing it to measurement If you do so then we can makethe

measurements and answer your question If you cant p ointtoany

observable dierences resulting from the existence or nonexistence of

atoms then you are just making meaningless sounds The solution to

your problem is for you to see the emptiness of your question

Some logical p ositivists thought that ethical and aesthetic judge

ments have no more meaning than emotional ejaculations Thus an

aesthetic judgementsuch as Thats b eautiful has the same content

as Wow or Nice An ethical such as Thats wrong

is really just an expression of p ersonal feeling like a snarl of anger a

hurt cry or a sympathetic moan If these haveany meaning at all it is

as reections of the sp eakers emotional state which is to b e reduced

to physiological measurements Thus A J Ayer says

For wehave seen that as ethical judgements are mere ex

pressions of feeling there can b e no way of determining

the validityofany ethical system and indeed no sense

in asking whether anysuch system is true All that one

may legitimately enquire in this connection is What are

the moral habits of a given p erson or group of p eople and

what causes them to have precisely those habits and feel

TLp ings Ayer L

Such aesthetic words as b eautiful and hideous are em

ployed as ethical words are employed not to make state

ments of fact but simply to express certain feelings and

evoke a certain resp onse It follows as in ethics that there

is no sense in attributing ob jectivevalidity to aesthetic

judgements and no p ossibility of arguing ab out questions

of value in aesthetics but only ab out questions of fact A

scientic treatment of aesthetics would show us what in

general were the causes of aesthetic feeling whyvarious so

cieties pro duced and admired the works of they did why

taste varies as it do es within a given so ciety and so forth

Ayer LTLp

THE VIENNA CIRCLE AND VERIFIABILITY

and the

Another imp ortant comp onent of logical p ositivism was the unity of



science movement Carnap gave a systematic of how in

general prop ositions expressed in the terms of one science say biol

ogy could b e reformulated into equivalent prop ositions in the terms

of another sayphysics Although the prop ositions of physics could

conceivably b e reduced to those of as well as the other wayin

practice it was assumed that physics would b e the ultimate goal of all

reductions

The thesis of maintains that the physical lan

guage is a language of science that is to saythat

every language of any subdomain of science can b e equip ol

lently translated into the physical language From this it fol

lows that science is unitary system within which there are

no fundamentally diverse ob jectdomains and consequently

no gulf for example b etween natural and psychological sci

ences This is the thesis of the unity of science Carnap

LSL p

Although the logical p ositivists were never able to carry out this pro

gram their legacy lingers on in many sciences in the form of a desire

to explain their phenomena in physical terms and of an acceptance of

the language and metho ds of physics as the standards of real science

an attitude sometimes called physics envy with acknowledged

Freudian allusions



Carnap LFUS is a clear explanation of the unity of science movementandthe metho ds of reductionism

CHAPTER LOGICAL POSITIVISM

The Collapse of Logical Positivism

Already by the s the logical p ositivist movement had b egun to

fragment Although this was the b eginning of the end the movement

continued for several decades and its attitudes and metho ds linger

to this dayinmany disciplines The causes of the collapse of logical

p ositivism can b e put in two classes internal weakness and external

criticism I will b egin with the internal causes

Nature of Atomic Facts

There were problems in the logical p ositivist program from the b egin

ning as there are in all new but they were exp ected to

b e easy to solve As it turned out they were fatal aws The rst

of these problems was the exact nature of the atomic facts which

were supp osed to b e the indubitable raw material of scientic theories

Ive mentioned that Russell changed his mind on this issue the logical

p ositivists were also unable to reach a consensus

AtrstSchlick to ok sense data to b e the atoms but he recognized

that sensory exp eriences are private there is no waytotellifthe

yellow I see is the same yellow that you see so sub jective sense data

seemed a bad foundation on which to build a supp osedly public ob jec

tive science Instead he decided to start from relations among sensory

exp eriences though our sub jective exp eriences of colors might dier

at least we might b e exp ected to agree ab out whether twopatches have

der relations among private the same color or not In this waytheor

sense data b ecame the raw material of theories as Schlick observed

you mighteven p erceive as pitches what I p erceive as colors but that

wouldnt matter so long as the relations among your p erceptions cor

resp onded to those among mine

However other memb ers of the Vienna Circle were not comfortable

with the abstractness of Schlicks solution since they wanted empirical

science to b e based on concrete Otto Neurath

prop osed protocol sentences as the atomic constituents of knowl

edge These were intended as incorrigible statements of facts which

would form the basis of theory construction This is one of his exam ples

THE COLLAPSE OF LOGICAL POSITIVISM

Ottos proto col at oclo ck At oclo ck Otto said

to himself at oclo ck there was a table in the ro om

p erceived by Otto Neurath PS p

Proto col sentences such as this seem to o complex to b e the atomic con

stituents of knowledge Nevertheless Neurath admitted that proto col

sentences are far from unambiguous He went so far as to suggest that a

term such as Otto could b e dened as the man whose carefully taken

photograph is listed no in the le Of course though this may re

duce the it do esnt eliminate it and in the end Neurath had

to admit that his proto col sentences are not incorrigible He thought

the truth of a proto col sentence could b e judged only by its coherence

with other proto col sentences and with the theories constructed from

them Sucha coherence theory of truth was anathema to the Vienna

Circle Therefore proto col sentences were judged insucient for the

ro cksolid foundation desired by the p ositivists

Ill mention just one more stage in this development to impress

on you the elusiveness of atomic facts Schlick countered Neuraths

prop osal with one of his own Wehave seen an incompatibilitybetween

incorrigibility and public veriabilityOnonehandwemay accept that

p ersonal sensory exp erience is indubitable but its absolutely private

On the other hand proto col statements are publicly veriable but are

inherently ambiguous and p otentially in error Schlick FK tried to

ysaying that a proto col sentence suchas combine the twob

MS p erceived blue on the nth of April at suchand

such a time and such and such a place

is just a that cannot b e counted as knowledge unless it has

a corresp onding conrmation sentencesuch as Here now blue How

ever as Schlick himself observed a conrmation statementcannotbe

written down since tokenreexive words such as here and now

In roughest terms a coherence theory of truth says that a system of laws

facts etc are true if they hang together well Crudely if its a go o d story then

its true Scientists as a rule are realists ie they b elieve there is a real world

indep endent of us as observers and therefore a should b e judged true

only if it corresponds to reality Crudelyinacorrespondencetheory of truth a true

sentence says whats so

CHAPTER LOGICAL POSITIVISM

lose there meaning But lling in a description of the time and place

converts it into a proto col sentence and incorrigibility is lost Thus

Schlicks analysis p ermits the individual scientist to havehisprotocol

sentences conrmed by private armations such as Here now blue

but this is not a satisfactory basis for publicly veriable science

Veriability Problems

Logical p ositivisms second ma jor internal problem was the status of

the veriability principle The p ositivists held that there were only

two classes of meaningful statements On the one hand were the an

alytic statements which express the truths of logic and mathematics

Since they follow necessarily from the axioms and denitions they are

indubitable but factually empty for they are consequences of the ax

ioms and denitions whichmaybechosen at will On the other hand

are synthetic statements whose truth dep ends on their verication In

rough terms wehave the truths of mathematics and the truths of sci

ence Anything that could not b e put into either of these categories

was necessarily metaphysical mumb ojumbo

The trouble with the p ositivists twoway classication of meaning

ful statements was that it seemed to leave no place for the veriability

principle itself On one hand it didnt seem to b e analytic and in

any case it wouldnt b e very convincing as a prescription if it were

merely a consequence of arbitrarily chosen axioms and denitions On

the other hand it could b e considered synthetic only if its meaning

What sort of could b e explicated in terms of verication conditions

measurements or observations could conrm the veriability principle

What if the observations when made disconrmed the principle The

p ositivists were also unhappy with this p ossibility

One solution would b e to conclude that the veriability principle is

a meaningful statement that is neither analytic nor synthetic But to

admit one meaningful statement thats neither analytic nor synthetic is

tantamount to admitting the meaningfulness of all the banished claims

of metaphysics The only alternativewas to admit that the principle is

factually meaningless and simply expresses certain feelings and evokes

a certain resp onse

For example Rudolf Carnap one of the ma jor gures of

THE COLLAPSE OF LOGICAL POSITIVISM

logical p ositivism see Carnap LSL xx distinguished state

ments that are in the material of speech that is ab out the world

from those in the formal mode of speech that is ab out language the

distinction is essentially the same as that b etween object language and

cf medieval ideas of and supposition p

The resolution of the problem of the status of the veriability princi

ple then lay in recognizing that its a statement in the formal mo de

of sp eech sp ecicallyitisa recommendation ab out how to use the

words meaningful and meaningless If you accept this recommenda

tion then you are b ound by the veriability principle and the rest of

the p ositivist view On the other hand if you do not accept it then

you have simply adopted another idea of meaningfulness you have

chosen to use meaningful and meaningless in a dierentway from the

p ositivists But this is no excuse for them to assert that you are sp eak

ing Carnap expressed this in his Principle of ToleranceIt

is not our business to up prohibitions but to arriveatconventions

Carnap LSL p In the end the aggressiveIfyou cant measure it

then you dont knowwhatyoure talking ab out had b een replaced by

the wishyw ashyWe recommend that you always base your denitions

on observables

Another problem with the veriability principle is that its strict

application would imply that no scientic law is meaningful For ex

ample wemayverify that Angus is mortal that Bridget is mortal and

that Camille is mortal but verication of all p eople are mortal is im

p ossible since it would require observation of an innite number of

cases The ma jor value of scientic laws lies in their applicabilityto

an innite numb er of situations yet it is precisely that prop ertythat

makes them strictly unveriable The logical p ositivists tried to escap e

this predicamentinmanyways but none were satisfactory For ex

ample some eg Schlick at one p oint said that in fact scientic laws

are technically nonsense though imp ortant nonsense This was not

a p opular p osition however and other p ositivists distinguished conr

mation or weak verication from strong verication the idea b eing

that the atomic facts can b e strongly veried and so are incorrigible

whereas general laws can b e conrmed by supp orting observations but

are not b eyond doubt and are always sub ject to empirical refutation

Unfortunately this p osition required giving up the certainty that p osi

CHAPTER LOGICAL POSITIVISM

tivism had promised Indeed Ayer LTLpwent so far as to declare

in that no prop osition other than a can b e anything

more than a probable hyp othesis Logical p ositivism had come a long

way

Another problem with the veriability principle was its exact in

terpretation Veriable means p ossible to verify but what is the

appropriate sense of p ossibility Logical p ossibility Physical p ossibil

ity Economic p ossibility For example Schlick raised the question

of the veriability of the prop osition that there are mountains on the

far side of the mo on Although at that time there were no ro ckets

capable of circumnavigating the mo on most p ositivists agreed that

the prop osition was veriable since they could see that it was veri

able in principle That is the necessary observations are theoretically

conceivable but the question remains of how far this theoretical con

ceivability can go For example I can conceive of devices that use

no energy such as Maxwells demon and therefore are physically

imp ossible Can myverication conditions make use of theoretically

conceivable pro cedures that violate the laws of physics

If our verication pro cedures are restricted to physically p ossible

then wehave the p eculiar situation that the meaningfulness of a sen

tence dep ends on the state of physical knowledge For example b e

fore when Heisenb ergs Principle was published the

prop osition that a particular particle has a certain sp ecic p osition and

momentum would ha ve b een meaningful since in principle p osition and

momentum could b e measured to arbitrary accuracyHowever in

the sentence b ecame meaningless since the says



that the supp osed verication pro cedure is physically imp ossible

Whenever one sees the sux able or ability its worthwhile to

ask What is the relevant sense of p ossibility

See Ayer LTL pp for further discussion of these issues



One also wonders ab out the precise way in which the meaning vanishes Do es

it disapp ear as so on as the Uncertainty Principle is formulated or only when it

b ecomes widely accepted Or do es it vanish for eachphysicist as they accept the

principle whichwould make meaningful sub jective Or do wediscover that the

prop osition was never meaningful whichwould mean we can rarely b e sure of mean

ingfulness since wemay revise at any time our b eliefs ab out physical p ossibility

THE COLLAPSE OF LOGICAL POSITIVISM

External Criticism

One must acknowledge the intellectual integrity and honestyofthelogi

cal p ositivists and their allies for it suered as much from their criticism

as from that of its enemies Weve seen that from the b eginning there

was disagreement ab out what should b e accepted as the incorrigible

givens the data that were intended to b e the atomic facts from

which true knowledge would b e constructed In addition to the contin

uing investigations of Russell Carnap and others the idea of atomic

facts was scrutinized in the s and s bysuch sympathetic philoso

phers as Tarski W V O Quine Nelson Go o dman and

Hilary Putnam However wepassover these criticisms since

they are subsumed by the more fundamental critique originating in the

phenomenological tradition which will b e considered in Chapter

An even more damaging assault came from the late Wittgenstein

J L Austin and other ordinary language philosophers

Since they will b e taken up in detail later Ch it will suce here

to say that they called into question the view of language that had b een

accepted through most of the Western philosophical tradition First

they p ointed out that the words of ordinary language do not have deni

tions in terms of essential characteristics as was generally assumed and

further that their meaning could not b e captured bysuch denitions

Therefore the metho d of logical construction was fundamentally inad

equate as a means of explicating metaphysical questions relating to

the mind consciousness p erception and so forth Second they showed

that the meaning of a statement in ordinary language is not a simple

function of the things denoted by its elementary terms as for exam

t ple in Tarskis semantic theory Sec Although each statemen

fullls a function for the community that uses it that function might

not b e the simple picturing of a state of aairs as early Wittgen

stein had held Although these conclusions followed from an analysis

of ordinary language it was apparent that they applied equally well to

much of scientic language see Ch so whatever logical p ositivism

might b e doing it was not explaining the actual practice of science or

extending it to other disciplines Finally the deep ened understanding

of meaning that came from ordinary language philosophyshowed that

the muchmaligned metaphysical statements are far from meaning

CHAPTER LOGICAL POSITIVISM

less As Putnam MLRVol p sadly remarked

Not a single one of the great p ositive theses of Logical Em

piricism that Meaning is Metho d of Verication that

physical prop ositions are literally without sense that Math

ematics is True byConvention has turned out to b e correct

Summary

So wemaysay that logical p ositivism came in with the bang of the

Tractatusbutwent out with the whimp er of increasingly rareed de

bates ab out atomic facts and the status of the veriability principle

Perhaps b ecause its quick birth was more visible than its slow death

remnants of logical p ositivism have lingered on in the sciences long after

most philosophers abandoned it

Inuence of Logical Positivism

Quantum

The Pythagorean scho ol was an osho ot of Orphism whichgoes

back to the worship of Dionysus Here has b een established the

connection b etween and mathematics whichever since

has exerted the strongest inuence on human thought The

Pythagoreans seem to have b een the rst to realize the creative

force inherent in mathematical formulations

Heisenb erg PP p

The inuence of logical p ositivist ideas is apparentintheCopen

hagen of quantum mechanics named for Bohrs Cop en

hagen Institute of Theoretical Physics where it was develop ed in the

mids mostly by and Werner Heisenberg

The Heisenb erg Uncertainty Principle one of the pillars

of quantum mechanics says that there is an unavoidable uncertaintyin

the measurement of certain conjugate variables such as p osition and

INFLUENCE OF LOGICAL POSITIVISM



momentum or time and energy Sp ecicallyifx is the uncertainty

in the p osition of a particle and p is the uncertainty in its momentum



then

x p h

Therefore if we increase the accuracy of our momentum measurement

wemust pay for it with decreased accuracy in the p osition measure



ment and vice versa

Although the Uncertainty Principle has b een very well conrmed

since it was rst prop osed in physicists still disagree ab out how

it is to b e understo o d The commonsense view whichwemight call

naive realist is that a particle actually has some sp ecic p osition and

momentum but that nature places limits on their joint measurement

This however is not the view of most physicists who endorse instead

the Cop enhagen Interpretation whichsays that since it is in principle

imp ossible to measure an exact p osition and momentum the particle

do es not in fact have them This can b e understo o d as a direct appli

cation of the Veriability Principle According to the laws of physics

ie Heisenb ergs principle it is imp ossible to verify a particles ex

act p osition and momentum so it is literally meaningless to sp eak of

it having an exact p osition and momentumWe can sp eak meaning

fully only ab out what we can measure Since we can measure only an

approximate p osition and momen tum it only makes sense to sp eak of



There is of course an enormous on the Uncertainty Principle b oth

p opular and technical by b oth physicists and philosophers My goal here is limited

to illustrating the ubiquity of logical p ositivist thinking in science Although quan

tum mechanics is not within the scop e of this b o ok its p erhaps worth remarking in

passing that the uncertainty relation can b e traced to the desire to have consistent

discrete particle and continuous wave descriptions of physical phenomena See

Heisenberg PP Ch for a readable discussion of the Cop enhagen Interpreta

tion



The exact constant Plancks constant h here dep ends on the way the measure

ment pro cess is dened



Its often thought that this uncertainty results from the measuring device dis

turbing the system but this is not the case for the uncertainty relation has b een

shown to hold even when the measurementismadebytheabsence of an interaction

socalled Renningerstyle measurements In fact the uncertainty relationship is

an inevitable consequence of the mathematics of quantum mechanics since it is a

of Fourier analysis that anyFouriertransform pair of variables eg time

and frequency will satisfy such a relationship Gab or TC

CHAPTER LOGICAL POSITIVISM

an approximate p osition and momentum as determined by the laws of

quantum mechanics

By taking p ositivism to its logical if absurd conclusion re

sp ected physicists have gone so far as to claim that its meaningless

to say that the mo on is still there when you are not lo oking at it

How could you observe that the mo on is there when its not b eing



observed

Positivism in Relativity Theory

Although Alb ert Einstein disagreed with logical

p ositivism and he published his rst pap ers on sp ecial and gen

eral relativity b efore the formation of the Vienna

Circle nevertheless we can see in them applications of the same



The dicultyphysicists haveaccounting for the collapse of the wavefunction

is also a consequence of their p ositivist approach with its dualist p ersp ective For

logical p ositivism separates the sub ject from the ob ject the observer from what is

observed As Heisenb erg PP p states explicitlyquantum mechanics starts

from the division of the world into the ob ject and the rest of the world and from

the fact that at least for the rest of the world we use the classical concepts in our

description

Since by the Cop enhagen Interpretation a particle cannot b e said to have a def

inite state until its observed to have a denite state it is said that b efore the

observation the particle exists as a sup erp osition of p ossible states but that after

the observation this sup erp osition collapses into a sp ecic state corresp onding to

what was actually observed It must b e emphasized that this collapse is required

only to account for the deniteness of observations The standard is that so

longasaphysical system is unobserved it continues to evolve as a sup erp osition

of p ossible histories On the other hand since the laws of physics are supp osed

to apply to everything in the universe including observers and their observations

one might exp ect there to b e a physical pro cess corresp onding to the collapse of a

sup erp osition of p otential observations into a single actual observation

This view generates a host of problems What is the nature of this collapse If it

is a physical pro cess what causes it If its caused by the act of observation what

constitutes an observation Must the observation b e made byahuman Or might

an animals awareness b e adequate to cause the collapse Could a machine make the

observation This line of reasoning has led to incredible conclusions such as that

consciousness had to evolve in the univ erse so that it would have a denite state

It also leads to a numberofparadoxes of which there are many p opular accounts

These vanish once one completely discards the dualism implicit in a

fundamental distinction b etween the observer and the observed MacLennan DD

INFLUENCE OF LOGICAL POSITIVISM

idea that physical concepts are constructions of observations

and that unveriable dierences are not real dierences In

Einstein directly acknowledged his debt to Mach saying the

study of Mach has b een directly and indirectly a great help in

mywork and Mach recognized the weak sp ots in classical me

chanics and was not very far from requiring a general theory of

relativity half a century ago quoted in Newman WMVol

p For example the p ostulate of relativity states there is

no exp erimentthatwe can p erform to distinguish one reference

frame from another that is moving at a constantvelo citywith

resp ect to the rst That is the terms absolutely at rest and

absolutely in are unveriable and hence meaningless

all that can b e veried is relative motion Similarly general rel

ativity is based on the p ostulate that an accelerating reference

frame is exp erimentally indistinguishable from a reference frame

in a gravitational eld This op ens the way for a geometrical

description of gravity in terms of the curvature of space

Behaviour is simply part of the biology of the organism and

canbeintegrated with the rest of the eld when describ ed in

appropriate physical dimensions

Skinner BSO p

Further evidence of the inuence of logical p ositivist thinking is

apparentinbehaviorism the that dominated

that eld through the rst half of the twentieth century and still exerts

a strong inuence Although the rst b ehaviorist manifesto Watson

predates the Vienna Circle B F Skinner one

of the principal exp onents of b ehaviorism traces its ideas to Mach

Poincare and Comte the same progenitors claimed by the logical

CHAPTER LOGICAL POSITIVISM

p ositivists Skinner BSO p Certainly b ehaviorism and logical

p ositivism b oth reect ideas in the air at the time

The founder of b ehaviorism was John B Watson who

b ecame dissatised with psychologys introsp ective metho ds while he

was a do ctoral student in the rst decade of the twentieth centuryAt

that time psychology as an exp erimental science distinct from philos

ophy had existed for only years and its principal metho d was to

ask observers to rep ort on their mental states which they had ob

served introsp ectively Watson thought that psychology could achieve

its goals b etter if it studied p eople the same way it studied animals

by observing overt b ehavior In this way psychology would b e more

scientic since it would make publicly testable predictions of b ehav

ior and it would b e more practical since it would pro duce means for

controlling b ehavior Watson describ ed his vision for a new psychol

ogy in summer lectures at Columbia in they were published the

following year Watson Although there were strong ob jections

from some quarters b ehaviorism advanced quickly Its hegemonyover

psychology from the s to the s can b e attributed in part to its

conformity with the contemp orary p ositivist philosophy of science but

also to its arrival on the scene just in time to sto ck the rapidly growing



psyc hology departments of the s and s

Behaviorisms emphasis on publicly observable b ehavior and its re

jection of introsp ection of mental states has much in common with log

ical p ositivisms rejection of metaphysics in favor of measurement

For example Skinner BSO p says

By dismissing mental states and pro cesses as or

ctions b ehaviorismdirects atten tion to the genetic and

p ersonal histories of the individual and to the currentenvi

ronment where the real causes of b ehavior are to b e found



Watson was left out of muchofbehaviorisms success As a result of a divorce

scandal he was shunned by academia and forced to earn a living selling rubb er

b o ots Eventually he was hired byanadvertising rm where he applied his knowl

edge of b ehavior to the developmentofmany of the techniques of mo dern advertis

ing Behaviorisms advo cacy of and technology for b ehavior control has inspired at

least three Huxleys Brave New WorldOrwells and Skinners Walden

Two See OCM sv Behaviorism and Cohen JBW

INFLUENCE OF LOGICAL POSITIVISM

Mental exp eriences such as a feeling of purp ose are epiphenomena

with no causal ecacy and the cause of our actions is to b e found in

the environment past or present

We do not act b ecause wehave a purp ose we act b ecause of

past consequences which generate the condition of our b o d

ies whichwe observeintrosp ectively and call felt purp ose

Skinner BSO p

Physics envy brings with it the assumption that everything of

imp ortance can b e measured so it is no surprise that Edward Lee

Thorndike who published his Measurement of Intel ligen ce

in was a leading b ehaviorist Of course there is nothing wrong

with trying to measure phenomena The problems arise when measure

ment is combined with the p ositivist outlo ok which tends to reject the

unmeasurable or even the unmeasured as meaningless and unimp or

tant Then the measured fragments of the come to b e

viewed as the whole of the phenomenon For example creativity seems

to have little correlation with the comp onents of measured

by IQ tests OCM sv Creativity but IQ is frequently treated as an



accurate measure of intelligence

The p ositivists emphasis on logical construction for example in

Carnaps logical is also manifest in b ehaviorist psychology

For example Clark Leonard Hull the leading b ehaviorist

of the s

wanted a theory of b ehaviour as formal as Euclids theory of

geometry and he intro duced and p ostulates which

could account for all b ehaviour OCM sv Behaviorism

p

tinues His intended b ehavior theory was not successful Debate con

ab out whether b ehaviorism improved psychology or merely delayed its

progress Be that as it may in the next chapter we will consider cog

nitive science a more sophisticated application of atomism and logical

construction in psychology



See Gould MM esp Chs for a discussion of the abuse of intelligence

measurements

CHAPTER LOGICAL POSITIVISM

The Turing Test

I b elieve that in ab out ftyyears time it will b e p ossible to



programme computers with a storage capacityofabout

to make them play the imitation game so wellthatanaverage

interrogator will not have more than p er cent chance of

making the right identication after veminutes of questioning

AMTuring CMI

Debate continues ab out whether a computer could think or havea

mind and conversely ab out whether the brain or mind is in some sense

a computer Often the discussion revolves around the Turing Test

whichTuring called the imitation game Turing CMI The topic

here is limited to the Turing Test as a reection of logical p ositivism

more general considerations will b e taken up later

Can machines think This is the question with whichTuring b egins

but he observes that the terms are not clearly dened He entertains

the p ossibility of capturing the everyday use of these terms in deni

tions essentially the metho d of ordinary language philosophy but

concludes that the result would have no more signicance than a public

opinion p oll Turing concludes

But this is absurd Instead of attempting such a denition

I shall replace the question by another which is closely re

lated to it and is expressed in relatively unambiguous terms

The new question is based on the imitation game First consider a

game played bya mana woman and an interrogator of either sex

The contestants are concealed from the interrogator who can com

municate with them only bytyp ed messages The ob ject of the game

for the interrogator to guess which contestantisthewoman the mans

ob ject is to fo ol the interrogator into thinking he is the woman the

womans ob ject is to convince the interrogator that she is in fact the

woman We can exp ect the interrogator to reach the correct conclusion

a certain fraction of the time probably more than half Now Turing

says supp ose we replace the male contestantby a computer so that

INFLUENCE OF LOGICAL POSITIVISM

b oth the computer and the woman are trying to convince the interroga

tor that they are the woman Turing says the original question Can

machines think can b e replaced by the question Can a machine



fo ol the interrogator at least as often as a human male contestant

As evident in the quotation that b egins this section Turing thought

that by the b eginning of the Twentyrst Century a computer would

pass the Turing test but we disregard that for now Here our concern

is not the answer to the question but how logical p ositivism inuenced

the formulation of the question

First observe that the Turing Test is completely b ehavioristic re

placing the mental think byaveriable b ehavioral pred

icate able to win the imitation game at least as often as a human

male

Turing acknowledges that passing the Turing test do es not prove

that the machine is conscious but he counters this with the wellknown

claim that we do not know if other people are conscious He observes

that Instead of arguing continually over this p oint it is usual to have

the p olite that everyone thinks He anticipates that rather

than retreating to a solipsistic p osition most p eople would b e willing

to extend this p olite convention to a Turing Testpassing machine

In other words Turing takes consciousness to b e a prop ertythat

is not publicly veriable and that is accessible only through introsp ec

tion Thus it has no role in his veriable surrogate for Can machines



think



Popular accounts of the Turing Test often have a p erson and a machine b oth

trying to convince the interrogator that they are the p erson the sexual comp onent

is omitted Though Turing do es not explain the purp ose for this extra complication

and most descriptions of the Turing test simply ignore it presumably it is to make

the test more fair by comparing the intelligence of twoagents in comparable tasks

imitating what they are not That is the goal is for the machine to knowasmuch

ab out b eing a woman as a man knows ab out b eing a woman but not necessarily

as muchasawoman knows ab out b eing a woman



Turings original pap er Turing CMI addresses many though not all of the

ob jections that have b een made against the Turing Test and machine intelligence

over the years and anyone interested in the topic would b e well advised to read it

and not dep end on this or any other secondhand account

CHAPTER LOGICAL POSITIVISM

Conclusions

The basic goals of logical p ositivism are laudable What we can say



we should say clearly who would argue with this Likewise a

question can often b e claried by asking Howwould you know Or

What dierence would it make And shouldnt we try to relate our

knowledge in one discipline to that in another and ferret out any in

consistencies These are common values in all intellectual activities

but esp ecially in science

The problems arise when these goals are pursued to extremes one

consequence of the quest for certaintyFor the logical p ositivists wanted

was an absolute free foundation for knowledge In this they

were no dierent from the rationalists of earlier times As empiricists

they diered in taking the ob jects of sense as their starting p oint rather

than the ob jects of the They were alike in supp osing they

knew where to nd absolute but when they tried to sieze

them they slipp ed through their ngers

The logical p ositivists ignored that fact that observation takes places

in a context a dense web of common practices eg measurement and

unstated assumptions eg As a consequence there are no

contextindep endent sense data nor are there observations unbiased by

preconceived ideas Further most signi concepts are not logically

reducible to necessary and sucient prop erties equivalent in turn to



their verication conditions Science progresses in spite of these dif

culties but they undermined the foundations of logical p ositivism

Though they ridiculed philosophys quest for metaphysical truth the

logical p ositivists fell prey to an equally alluring idea and naively as

sumed the existence of contextfree atomic facts Nietzsche foresaw

the trap

wever go still further and also declare war re One must ho

lentless war unto death against the atomistic need which

still leads a dangerous in places where no one sus



In fact there are situations b oth so cial and legal in whichintentional ambiguity

is desirable We ignore this for now and restrict our attention to scientic and

philosophical where presumably clarity is always desirable



These issues will b e discussed in more detail in Chap

INFLUENCE OF LOGICAL POSITIVISM

p ects it just like the more celebrated metaphysical needNietzsche

BGE x

One unfortunate consequence of logical p ositivism which still in

fects those disciplines where it has b een inuential is the dogmatic

intolerant arrogant and closedminded attitude that it encourages For

when p eople are certain they are correct they tend to b e intolerantof

other p oints of view Why compromise with falseho o d And so we

often nd physics envy reinforced by physics arroganceIfyou dont

do things likewephysicists saywe do things then you arent a real



scientist

One common form taken by this arrogance is the dogmatic limita

tion of phenomena to the measurable Certainly there is no inherent

harm in trying to measure things the mistake comes in the assumption

that such observational or pragmatic correlates exhaust the phenom

ena Thus we hear Intelligence is what IQ measures Other imp or

tant but unmeasured comp onents of intelligence are simply dened out

of existence and therefore disvalued

In conclusion the ma jor value of logical p ositivism as of rational

ism and other singleminded views may b e that it exp osed

its own limitations Now that wehave thoroughly explored that path

we can turn our attention to others



As a consequence many soft sciences and wouldb e sciences try to emulate

the metho ds of physics to excess For example has engendered

the largely unfruitful software physics and software science