## 1. Biographical Sketch




Alfred Jules Ayer was born in London on October 29, 1910. His mother,
Reine, was descended from Dutch Jews, whilst his father, Jules Louis
Cypress Ayer, came from a Swiss Calvinist background. As recounted in
Rogers 1999, Ayer was a precocious but mischievous child, and so was
sent to boarding school (outside Eastbourne) at the age of seven, from
which he won a scholarship to Eton in 1923. There he impressed his
peers with his intelligence and competitiveness, the latter trait
manifesting itself in the way he played games. Ayer nevertheless felt
an 'outsider', and it is clear that his fellow-students
did not warm to him, perhaps due to the excessive zeal with which he
attempted to convert them to atheism. Feeling 'an
outsider' was something that remained with him all his life. At
the age of sixteen he specialized in classics and at the same time
started reading some philosophy. Bertrand Russell's
*Sceptical Essays* made an impression, particularly Russell's
argument for the claim that it is undesirable to believe a proposition
when there is no ground for believing its truth. Ayer said that this
remained a motto for him throughout his philosophical career (see
Rogers 1999, 45). At the same time a reading of G.E. Moore's *Principia
Ethica* also had a lasting effect, particularly Moore's
articulation of the Naturalistic Fallacy.




The Easter before leaving Eton, Ayer spent some time in Paris, where he
met Renee Lees, whom he subsequently married (in 1933). The following
year (1929) he won a classics scholarship to Christ Church, Oxford,
where he studied both Greek and philosophy, one of his tutors being
Gilbert Ryle. It was Ryle who suggested that Ayer read Ludwig Wittgenstein's
*Tractatus Logico-Philosophicus*, a work that immediately
impressed him. Ryle was also instrumental in getting Ayer to go to
Vienna in 1933 to study with Moritz Schlick, then leader of the
influential Vienna Circle of philosophers, scientists and other
intellectuals, joining W. V. O. Quine in being one of only two
visitors to be members of the Vienna Circle. His philosophical
experience in Vienna was somewhat limited by his uncertain knowledge
of German, but he knew enough to pick up the basic tenets of logical
positivism.




After leaving Vienna, Ayer lectured for a short time at Christ Church,
where in 1935 he was elected to a five-year research fellowship. In
the same year he finished *LTL*, which caused a great deal of
controversy and debate, partly for its sweeping dismissal of
metaphysics, but especially for the metaethical emotivism Ayer
championed in one of its most notorious chapters. During the next few
years, Ayer worked at defending and refining some of the positions
adopted in *LTL*, not least at meetings in Oxford with Isaiah
Berlin, Stuart Hampshire, and J.L. Austin; the confrontations with
Austin were to prove long-lasting. The product of this refining
process was the book *Foundations of Empirical Knowledge.*
During this time he also enjoyed life to the full; he was a good
dancer, once confessing that he would have preferred to be a
tap-dancer rather than a professional philosopher, but had given up on
the idea when he recognized that he would never be as good as Fred
Astaire. His marriage to Renee started to disintegrate; Ayer had
numerous affairs, and Renee formed an enduring relationship with
Stuart Hampshire.




In the immediate pre-war years, Ayer had become passionate about
politics. He supported the Republican side in Spain, flirted with
joining the Communist Party, but instead became an active member of
the Labour Party. When war was declared he joined the Welsh Guards
(and was helped to do so by Gilbert Ryle). He worked for a while in
Cambridge interrogating prisoners, then was sent to America to join a
secret service mission, one which seemed to involve gathering
information about Fascist sympathizers in America. Whilst in New York
he reviewed films for the *Nation*, fathered a daughter (Sheila
Graham was the mother), and made a record with Lauren Bacall. On being
repatriated to England, Ayer found himself given the job of helping
with the organization of the French resistance movements in
London. Shortly after the war he was posted to Paris, where he took
the opportunity to study French existentialism, writing articles on
Sartre and Camus in *Horizon*.




On his release from Army service Ayer accepted the offer of a tutorial
fellowship at Wadham College, Oxford, but was there only a short while
before becoming the Grote Professor of Philosophy at University
College, London, at the age of 36. He quickly appointed Hampshire to a
lectureship (making up for having cited Hampshire as co-respondent in
his divorce from Renee), then Richard Wollheim. The department grew
and became a thriving philosophical center. Ayer also ventured into
the world of radio, being involved in many BBC Third Programme
broadcasts, including panel discussions with the scientists Zuckerman,
Huxley and Medawar, and a famous debate with the Jesuit priest
Frederick Copleston on the existence of God. Later he became a regular
performer on BBC television's "The Brains Trust". In
1948 he lectured at Bard College in New York, but it proved to be an
unhappy experience. Back in London C.E.M. Joad had published an
article in the
*New Statesman* arguing that *LTL* was responsible for
creating an environment in which Fascism flourished, and *Time*
magazine published an unflattering short article claiming that Ayer
taught his students that "That man is good to support his
mother" was a meaningless statement (Rogers 1999,
p. 232). On his return to Europe he started a hectic schedule of
lecture tours, visiting France, Belgium, Italy, Sweden, Denmark, Peru,
Chile, Uruguay, and Brazil, all in the early 1950s.




In 1958 Ayer took the opportunity to return to Oxford as Wykeham
Professor of Logic. He later said that this decision was made in order
to combat the growing influence of Austin, who had made a point of
attacking Ayer's views on perception. Austin was, however, soon
to die, making Ayer's 'sacrifice' of his life in
London somewhat pointless. Not that it was completely sacrificed; he
bi-located, spending long weekends in London with his second wife, Dee
Wells, and at most three nights in New College during the week. He
continued to travel widely: China, Russia, India, and Pakistan were
added to the itinerary. He also continued his political activity,
continuing to support the Labour Party, campaigning against British
involvement in Vietnam, and being at one time Vice-President of the
Society for the Reform of the Abortion Law, Chairman of the Campaign
Against Racial Discrimination in Sport, and President of the
Homosexual Law Reform Society. His support for the decriminalization
of homosexual behavior, he once quipped, could not be thought by
anyone acquainted with him to involve a vested interest. Ayer's
support for the Labour Party came to an end with the formation of the
Social Democratic Party in 1981. His support for the SDP was a protest
at the leftward trend of the Labour Party, and particularly its
anti-Europeanism.




The arrangement of spending long weekends in London and some of the
working week in Oxford added to Ayer's turbulent domestic
life. In 1963 he and Dee Wells had a son, Nicholas, of whom Ayer said,
"My love for this child has been a dominating factor in the
remainder of my life" (Rogers 1999, 278.) He formed a relationship
with Vanessa Lawson, whom he would see whilst in Oxford. During this
time, Ayer continued to be philosophically productive,
doing some of his most original work. *The Origins of
Pragmatism* was published in 1968, following this *Russell and
Moore: the Analytical Heritage* (the product of the William James
lectures he delivered at Harvard in 1970), and *Probability and
Evidence* (the Dewey lectures delivered at Columbia University in
1970). Shortly thereafter came *Russell*, a small paperback,
and *The Central Questions of Philosophy* (1973, originally
given as the Gifford Lectures at the University of St. Andrews), in
which he elaborated on the sophisticated realism first put forward in
*The Origins of Pragmatism.* He visited Canada on a couple of
occasions, giving the Gilbert Ryle lectures at Trent University (1979)
resulting in his book on Hume, and the Whidden lectures at McMaster
(1983) giving rise to *Freedom and Morality*.




Shortly after being divorced from Dee Wells, Ayer married Vanessa
Lawson in 1982. Shortly before that Renee, his first wife, had died
(1980), followed by Valerie, their daughter, who died suddenly of
Hodgkin's disease in 1981. Tragically Vanessa was to die of liver
cancer in 1985, leaving Ayer grief-stricken. He himself had a close
encounter with death, being 'technically' dead for a few
minutes after choking on a piece of smoked salmon. On reviving he
reported his experience whilst 'dead' in such a way as to
provide fodder for those who thought the famous atheist had recanted
and found God. He moved quickly to dispel these rumours. By this time
he had become something of a philosophical Grand Old Man, with volumes
published in his honour, and a full-length critical study by John
Foster in the prestigious Routledge "arguments of the
philosophers" series. He spent most of the remaining couple of
years responding to articles that were to appear in the Ayer volume in
the Library of Living Philosophers series, edited by L.E. Hahn. He
remarried Dee Wells, but not long afterwards Ayer was admitted to
hospital with a collapsed lung in the early summer of 1989 and died on the
27th, June.




Ayer wrote two autobiographies, *Part of My Life*, and *More
of My Life*. His circle of friends included many famous and
influential people; the following (in no particular order) is only a
brief list. Cyril Connolly, Graham Greene, George Orwell, ee cummings
and his wife Marianne, Meyer Schapiro, Arthur Koestler, Bertrand
Russell, Stephen Spender, W.H. Auden, Philip Toynbee, Isaiah Berlin,
Hugh Gaitskell, Roy Jenkins, Michael Foot, Richard Crossman, Jonathan
Miller, Angus Wilson, Alan Bennett, Alice Thomas Ellis, Joan Fontaine,
Iris Murdoch, V.S. Pritchett, and Christopher Hitchens. He believed,
maybe truly, that the character of George Moore in Tom
Stoppard's play *Jumpers* was modeled on him. Ayer was a
vain man whose vanity was part of his considerable charm. He made a
distinction between vanity and egotism; an egotist, he said, thought
he should have more medals, whilst a vain person just enjoyed showing
off the medals he had. Among the many 'medals' given to
Ayer were his knighthood, Fellow of the British Academy, honorary
member of the American Academy of Arts and Sciences, Member of the
Bulgarian Order of Cyril and Methodius, 1st class, and
Chevalier of the Legion d'honneur.


## 2. Meaning and Truth


### 2.1 Meaning




The empiricist basis of Ayer's attitude to meaning was laid first in
his reading of Hume. The thought that no idea had any empirical
significance unless it was suitably related to an impression stayed
with him, and was reinforced both by his reading of Wittgenstein's
*Tractatus* and by the time spent in Vienna with the Logical
Positivists. His first formulation of a criterion of meaning, the
principle of verification, was in the first edition of *LTL*
(1936)*,* where he claimed that all propositions were analytic
(true in virtue of their meaning) or else either strongly verifiable
or weakly verifiable. Strong verification required that the truth of a
proposition be conclusively ascertainable; weak verification required
only that an observation statement be deducible from the proposition
together with other, auxiliary, propositions, provided that the
observation statement was not deducible from these auxiliaries
alone. This rapidly proved defective: any proposition *P*
conjoined with 'if *P* then *O*', where
'*O*' is an observation statement, will yield
*O*, without this being deducible from 'if *P*
then *O*' alone. So in the second edition Ayer amended
the principle to read: a statement is directly verifiable if it is
either an observation statement or is such that an observation
statement is derivable from it in conjunction with another observation
statement (or observation statements), such derivability not being
possible from the conjoined observation statement(s) alone. And a
statement is indirectly verifiable if, first, in conjunction with
certain other premises it entails one or more directly verifiable
statements that are not derivable from these other premises alone,
and, second, that these other premises "do not include any
statement that is not either analytic, or directly verifiable, or
capable of being independently established as indirectly
verifiable." (*LTL* 2nd ed. P. 17).




This principle generated further criticism, most significantly from
Alonzo Church (1949), who claimed to show that, again, it allowed
*any* statement to be meaningful. Take *O*1,
*O*2, and *O*3 as logically
independent observation statements, and *S* any statement
whatsoever. Then




(1) (!*O*1&*O*2) v
(*O*3&!*S*)




is directly verifiable, as (1) in conjunction with
*O*1 entails *O*3. *S*
becomes indirectly verifiable, as *O*2 follows from
*S* and (1), and (1) is directly verifiable. Should
*O*2 follow from (1) alone, then
*O*2 follows from
*O*3&!*S*, which means that
!*S* is directly verifiable (*O*2 and
*O*3&!*S* being logically
independent).




Despite the failure of these attempts to provide a rigorous empiricist
criterion of meaning, Ayer continued to hold that there was a close
connection between evidence and meaning, maintaining that a
satisfactory account of confirmation was needed before a fool-proof
criterion of empirical meaning could be supplied. Given later doubts
about whether any theory of confirmation could provide a foundation
for a theory of meaning (Quinean doubts relating to the impossibility
of ruling out any facts as possibly bearing on the truth of any
sentence), it remains unclear as to how the evidence-meaning
connection can be circumscribed. (For a review of other attacks on,
and adjustments to, the verification principle, see Wright 1986,
1989.)


In addition to the technical difficulties surrounding the proper
formulation of the meaning-criterion, Ayer later acknowledged that he
had been vague as to whether the criterion was intended in a 'weak' or
'strong' sense: if weak, verifiability merely demarcated sense from
nonsense, whilst the strong version meant that the method of
verification provided the meaning of the sentence. It was the strong
version that was used in his discussion of the meaning of sentences
about the past and other minds, but in his discussion of the latter
another difficulty emerged. It had not been made clear whether the
'method of verification' was intended to be neutral between people
employing the sentences in question, and so provide a standard meaning
for these sentences, or whether such a method could provide an
idiosyncratic meaning for one individual's use of the sentence, the
method of verification being peculiar to that person. In his
discussion of mental experiences, Ayer had implicitly taken the second
route, and so sentences attributing such experiences to himself were
given a 'mentalistic' analysis, and those attributing experiences to
others were given a behaviorist analysis (see the introduction to the
second edition of LTL. At the same time, however, he construed
another's self-attribution of experience mentalistically, whereas, as
he later acknowledged, to be consistent these should also have been
given a behaviorist analysis (see the discussion between Bernard Williams and
Ayer in Macdonald 1979).




The strong interpretation of the criterion required there to be some
decision made as to what evidence contributed to the meaning of
verifiable sentences. For Ayer it was clear that not all evidence for
a statement was to be included in the meaning of the statement: a
statement about the blood on Jack's jacket was not included in the
meaning of the assertion that Jack was the murderer. Further, although
only present evidence is available to anybody making a statement about
the past, the meaning of such a statement is not restricted to such
present evidence; one is entitled to include in the meaning evidence
that would be available if one were able to transport oneself to that
past time. Moral statements were, in Ayer's view, not verifiable, and
so could not be construed as assertions of fact, being interpreted
instead as expressions of emotion. This is examined again in Section
7.




The only class of statements that Ayer allowed to be meaningful
without such a connection to evidence was that comprised of
tautologies, which included all analytic propositions. These were the
only propositions knowable *a priori*, their meaning being
dependent on how language was used, and on the conventions governing
that use. Ayer insisted that the necessity attaching to these
propositions was only available once the conventions governing
language-use were in play.


### 2.2 Truth




In *LTL* Ayer, following Ramsey (as he thought, but see Field
1986 for a dissenting view), put forward a redundancy (deflationary)
view of truth: "...in all sentences of the form
'*p* is true', the phrase 'is true' is
logically superfluous" (*LTL* p. 117). The function of
such a phrase is simply to mark an assertion (or denial, in the case
of 'is false'), so there is no 'real' relation
of truth, and so no problem of truth for philosophers to worry
about. Similarly, when we say a proposition is probable, or probably
true, we are not assigning any intrinsic property to the proposition,
nor saying that there is any relation it bears to any other
proposition. We are simply expressing our confidence in that
proposition, or, more accurately, it expresses the degree of
confidence it is rational to possess in the proposition.




This deflationary attitude to truth was supported by his
verificationism about meaning; Ayer did not have to provide
truth-conditions for the meaning of sentences. Assertions had meaning
in virtue of their verification conditions, and propositions were
defined just as an equivalence class of sentences with the same
verification conditions.




Deflationism about truth replaces a concern for a substantial theory
of truth with a concern about which sentences, or utterances, are
deemed to be truth-apt. Ayer denied that moral utterances were
truth-apt. Given that he thought that asserting that *p* was
equivalent to saying that *p* was true, he had to deny that
moral utterances could be assertions (see section 7).




See the entry
 on the deflationary theory of truth
 for further discussion.


## 3. Perception




In his early work on perception Ayer espoused a strict form of
phenomenalism, defending the view that statements about material
objects are translatable into statements about actual and possible
'sense-contents'. These latter statements were the
ultimate verifiers, forming the basis upon which our empirical world
was constructed. Although he later abandoned the reductionism inherent
in the translatability requirement (beginning with
"Phenomenalism" in 1947), believing that he had been wrong
to think that any statement about a physical object could be entailed
by a set of statements about sensory experience (sense-data), Ayer
continued to hold that our claims about physical objects were
justified by reference to such sensory experience. He consistently
opposed the view, espoused by Rudolf Carnap, Otto Neurath, and Karl
Popper, that the only justifiers were sentences, whether
Neurath's 'protocols' or Popper's 'basic
statements'. His criticism of such views was that the favoured
class of statements could not be picked out in the right way without
an appeal to relevant experience. So a criterion for membership of the
favored class of statements that required only those statements
accepted by the scientists of the time to be members of the class was
not going to be successful without knowing which sentences were thus
accepted, and this, Ayer claimed, could only be known by
experience. The alternative of using yet another sentence, one stating
that these (*p*,*q*,*r*, ...) were the
sentences in the relevant class (those accepted by the scientists),
would make the foundations of science entirely arbitrary.




Even on Ayer's later view, called 'sophisticated
realism'(in Ayer 1973), where our perception of physical objects
was indirect, the ultimate bases for perceptual judgments were
sense-data, which were now called 'qualia' (or, if
particularized, 'percepts'). It was this continuing
commitment to sense-data as the objects of perception that drew J.L.
Austin's (often sarcastic) criticism in *Sense and Sensibilia*
(1962). On Ayer's view, qualia formed the patterns constituting a primary
system, and it was on the basis of this system that we posited the
existence of physical objects, this being the
'theoretical' secondary system. Once we have this theory,
we are able reinterpret the quale as mental states and claim that they
are caused by the physical objects. This causal claim is only merited
once the theoretical system is in place, and so cannot be a primitive
element in any account of perception. The physical objects are
required to be there before any causal hypothesis involving them makes
sense.




Part, but only a part, of Ayer's reason for embracing such indirect
realism was what has been called the argument from illusion, the
central idea of which is that, for any perceptual state of ours, we
could be in a state indiscriminable from it but which did not involve
perception of any material object or scene, it being an illusion that
there was any such object or scene to be perceived. That is,
non-veridical perceptions could share their intrinsic properties with
veridical perceptions, this possibility leading Ayer to claim that it
was plausible that the object of perception in both cases was
(non-material) experience, and not, as naive realism would have
it, the physical objects themselves. As a consequence, ordinary
perceptual judgments, those making claims about such objects, go
beyond what is 'strictly available' in our perceptual
experience, and so they form a theory about that which is available to
perception.




There are many ways of querying Ayer's conclusion. Austin attacked the
way he saw the argument from illusion being deployed. He questioned
just about everything in it: the distinction between veridical and
non-veridical perception, the supposed generalization from 'some
(real) perceptual experience is indiscriminable from a (mere)
perceptual appearance' to 'all such perceptions are
indiscriminable from their counterpart appearances', and the
assumption that when we have defective perceptions there are
non-material objects of those perceptions, sense-data.




Strawson (1979) argued that the primary system, that purporting to
describe no more than what was 'strictly available' to
perception, could only be described using concepts available to those
already acquainted with the secondary system. A consequence of this,
he claimed, was that the secondary system embodied in ordinary
perceptual judgments could not be a theory with respect to which the
primary system was the data - the data have to be describable in
terms that do not presuppose the very theory for which they are the
data. Although, he argued, it may be possible, though difficult, for
us to strip our vocabulary describing our experience of such
secondary-system concepts, such an effort on our part would be
unusual, and not at all like what is involved in our common-sense
perceptual judgments, those that Ayer supposes to be the result of
some theorizing on our part. For Strawson, our commitment to a
conceptual scheme of a realist character is 'something given
with the given' (Strawson 1979, p. 47).




Ayer was unmoved by the objections. He replied to Austin's attack in
"Has Austin Refuted Sense-data Theory" (Ayer 1967), with
Ayer defending the viability of the distinction between veridical and
non-veridical perception, and maintaining that the argument from
illusion was only one source of the case for sense-data. (For an
in-depth discussion of the dispute between Austin and Ayer, see Mike
Thau, "What is Disjunctivism" 2004). Against Strawson
("Replies" 1979) he noted that there was considerable
agreement between them: in particular, they both agreed that
perceptual judgments contain implications going beyond those carried
by a 'strict' account of our sensible experience. The
disagreement was primarily about whether the perceptual judgments were
based on, or were inferred from, awareness of sense-data. Ayer
conceded that such an inference would be only implicit. The point
about language he conceded as well, maintaining only that the
assumptions often built into concepts descriptive of physical objects
- the accessibility of such objects to other observers, that
they continued to exist unperceived, and so on, would not be in play
when these concepts were used to provide the 'strict'
account of perceptual experience.


## 4. Induction and Probability




Hume was an influential figure in the formation of Ayer's
philosophical views, so it is no surprise to find Ayer's approach to
inductive inference modeled on Hume's. Ayer defined inductive
inference in negative terms, as involving all factual inference in
which the premises did not entail the conclusion. All such inferences,
Ayer claimed, presumed the uniformity of nature, an assumption he put
in terms of assuming that the future will, in relevant respects,
resemble the past (1956, p. 72). To unambiguously cover cases of
retrodiction, the assumption is better put in terms of the unobserved
resembling, in relevant respects, the observed. Ayer agreed with Hume
that relying on any 'principle' of the uniformity of
nature was not going to help justify inductive inference, given that
such a principle was itself not demonstrable. A similar argument
applied to any other principles that may have been thought to supply
the missing ingredient, such as an appeal to universal causality, or
to laws of nature. These were also not demonstrably true, so would
require justification themselves, and any appeal to these principles
in such a justification would be viciously circular.




The fundamental problem here is that the inductive gap can be closed
only if the premises can somehow be made to entail their conclusion,
and Ayer denied that this could be done. Naive realism tried to
do it by making the evidence 'move up' to the conclusion
- by making it the case that in perception our evidence was
directly of physical objects, rather than of sense-data from which
physical objects were inferred. This could work, if it did, only for
perception, and not for other inductive inferences. Reductive attempts
to close the gap tried to make the conclusion 'move down'
to the premises, as in phenomenalism. Ayer by now thought
phenomenalism was unsuccessful in this attempt, and again reductionism
would not work for the future cases. In his 1956 he thought that the
best we could do was to admit the gap and be content to describe the
ways in which we actually went about justifying such inferences.




Ayer went on in later work to examine the problem of induction in
greater detail, in particular in relation to attempts to make the
problem tractable by appeal to notions of probability. In 1957 he
wrote an important article attacking the idea that the logical
conception of probability could be a useful guide to the future. Given
a proposition, *a*, that a horse is going to win the race, and
various sources of evidence, *h*1,
*h*2,
*h*3...*h*n, one can estimate
the probability of *a* given *h*1 to be
*p*1, given *h*2 to be
*p*2, and so on. One can also estimate the
probability of *a* given all of *h*1
...*h*n. Call this probability
*p*n, it being the probability of *a* given
all of the evidence available to the person wishing to place a bet on
the horse. Which of these probabilities, asks Ayer, would it be
rational for this person to base their bets on? Common sense dictates
that *p*n is the best estimate, but Ayer argues that
on the logical conception of probability, all of the estimates
*p*1...*p*n are logically
true, and so it is impossible to single out one as being
'better' than any of the others.




Ayer notes that common sense (and Carnap) say that a probability based
on 'total' evidence is what is needed. But why do we have
to take into account total evidence? Given that all of the different
estimates are logically true, there can be nothing wrong in relying on
one rather than another. Saying that if one takes into account all the
available evidence one is more likely to be right is equivalent to
saying that the hypothesis that 'those with total
evidence' are more often right has a certain probability, and
that gets us no further forward. Ayer took this result as a reason to
reject the logical interpretation of probability statements, a
rejection repeated in his more extended treatment of probability in
*Probability and Evidence* 1972, and again in his reply to J.L.
Mackie's attempt to rebut his objections (see Mackie 1979, Ayer
1979).


In *Probability and Evidence* Ayer also criticised the
frequency interpretation of probability, noting that under this
interpretation the probability of an event will change with any change
in the reference class to which that event is assigned. The frequency
interpretation itself cannot determine whether the choice of one
reference class over another is better for the determination of the
relevant probability, and so suffers from a critical defect if it is
to be of any use in solving problems associated with inductive
inference. (For further discussion of Ayer's views on probability and
induction see Bela Juhos 1969, and Foster 1985, pp.198-227.)


## 5. Knowledge




In *The Problem of Knowledge* (1956), Ayer defended a
context-based account of knowledge that had as its essential
ingredients that some claim, *p*, counted as knowledge for a
person, *A*, *iff* *p* was true, A was sure that
*p*, and *A* had, in the relevant context, 'the
right to be sure' about the truth of *p*. The contextual
element is apparent in the discussion after Ayer outlines what is
required to have the 'right to be sure' in the
mathematical case. One avenue to knowledge in this case lies in the
ability of the agent to provide a proof of the relevant
proposition. In the case of perception, or memory, it is clear that it
is impossible to possess such a proof, so a more relaxed standard is
required. To state *in general* how strong the backing needs to
be for a believer to have the right to be sure that their belief is
true is not possible; doing so would require drawing up a list of
conditions "under which perception, or memory, or testimony, or
other forms of evidence are reliable." (1956, p. 32.) Ayer
thought this would be too complicated a task, if at all possible. The
'correct' standard to set for claims to knowledge is to be
decided pragmatically, on grounds of practical convenience. The
skeptic's ploy of setting an impossible standard, one requiring the
impossibility of error, should be resisted, as one has the right to be
sure even where error is possible.




The account offered was intended as an analysis of knowledge, but
revealingly Ayer did not require that believers be aware of how they
have the right to be sure. It was allowed that somebody who invariably
correctly predicted the outcome of a lottery *could* be said to
know that their prediction was true, even though they, nor anyone
else, had any idea of how the predictions came to be reliable. Ayer
admitted that this case, and others like it, may cause some dispute:
it was not clearly covered by the meaning of the term
'knowledge', and so left room for some stipulation.




Ayer's particular analysis, or one closely resembling it, came
under attack in a famous paper by Gettier (1963), in which
satisfaction of the three clauses (the truth of *p*, the belief
in *p*, and the right to be sure that
*p*) was held to be insufficient for knowledge. Gettier's
argument requires that someone, *A*, could be justified in
believing a false proposition, and that if *A* was justified in
believing *p* and *q* is deducible from *p*, and
*A* accepted *q* by deducing it from *p*, then
*A* would be justified in believing *q*. An example used
by Gettier has the following structure: (i) Jones owns a Ford. (ii)
Either Jones owns a Ford or Brown is in Boston. Smith believes, and
has ample evidence for, (i). He deduces (ii) from (i), and so is
justified in believing (ii), even though, in fact, he has no idea of
where Brown is. It turns out that (i) is false, but (ii) is true
- unbeknownst to Smith, Brown is indeed in Boston. Gettier
concluded that in this case all three clauses of the analysis of
knowledge are satisfied, but that we should judge in this case that
Smith did not know (ii). The suggestion was that additional clauses might be needed.




The literature spawned by the Gettier counter-examples is huge, nearly
all of it attempting to pin down the elusive additional
clause(s). Ayer himself did not think that any such additional clauses
were needed. The counter-examples, he thought, showed that what was
needed was a more careful account of what 'being
justified' consisted in. He disputed Gettier's claim that any
deduction from a justified, but false, proposition preserves
justification. We already knew, he claimed, that the notion of having
evidence for a claim is very difficult to elucidate; Carl Hempel's
paradoxes succeeded in showing that. Once we had managed to throw more
light on the justification relation, we would see that his proposed
analysis was sufficient for knowledge.


## 6. Necessity, Causality, and Freedom




We have seen that in *LTL* Ayer maintained that all necessary
truths were true in virtue of the meanings of the terms used in
expressing them, this in turn depending on the conventions governing
the use of those terms. One can see in the expression of this early
view unease about the source of logical necessity. He describes the
necessity of logical truths as dependent on the rules governing the
use of logical constants. Although such rules are neither true nor
false, they elucidate the "proper" use of such constants,
a formulation suggesting that the source of the necessity is deeper
than mere linguistic usage.




Later, cleaving (or perhaps clinging) to his "all necessity is
*de dicto*" starting point, he consistently refused to
countenance any *de re* necessities. He strenuously resisted
the essentialism that became fashionable following the work of Putnam
and Kripke in the 1970s, but his reasons for doing so were not always
to the point. In his argument against essence-based *de re*
necessities Ayer would say that "Caesar is necessarily
human" is not true, since he could have called his dog
"Caesar". Here he lost sight of his own insistence (in the
Introduction to the 2nd. Edition of *LTL)* that
necessary truths were expressed in a language whose terms had already
been assigned meaning and reference, so changing the reference of
"Caesar" is irrelevant to the necessary truth of a
sentence employing the term with its 'normal'
reference.




Of greater relevance was his suspicion of the move from conceivability
to possibility, and inconceivability to impossibility, thinking that
answers to questions about conceivability were dependent upon the
state of knowledge and imaginative powers of the person entertaining
them. Was it inconceivable that Caesar (the Julius of old) be
non-human? Ayer thought it consistent with everything he knew of
Caesar (apart from his being human) that Caesar was a robot, so he
could "easily conceive of it as a possibility"
("Replies" p. 308). On the other hand, if asked whether
Caesar was a tortoise, he would suspect that the word
"Caesar" was here used with a different reference in mind.
Ayer buttressed this thought by suggesting that the descriptions
securing the referent of the term "Caesar" would normally
make it logically inconsistent that the satisfier of the descriptions
be a tortoise, but that this did not establish *de re*
necessities; it does not follow that the Caesar in question
*necessarily* satisfies the descriptions associated with the
use of the name. To the suggestion that something other than
descriptions might secure the proper reference, such as the causal
origin of the use of the term, Ayer was dismissive: "...the
idea ...that one can explain the nature of reference by saying
that what makes *A*'s use of a sign *s* a
reference to an object *O* is its causal derivation from
someone's original use of *s* to refer to *O* is a
manifest absurdity. If one does not understand what it is for
*s* to refer to *O*, one is none the wiser; and if one
does, the causal flummery is otiose." ("Replies"
1979 p. 309.)




Ayer's rejection of these kind of *de re* necessities was, at
root, a consequence of his epistemological approach to their
evaluation. The senses of terms, he thought, were dependent on their
associated descriptions, these being dependent on what we knew of
their reference, and these senses accounted for the presence or
absence of necessity. So it is identity of sense in "Hesperus is
Hesperus" that makes that sentence necessarily true, whilst
absence of sense-identity renders "Hesperus is
Phosphorous" contingently true. He rejected the thought that
natural kind terms have their sense fixed by their internal
constitution on the grounds that many, if not most, users of natural
kind terms are ignorant of the nature of the relevant internal
constitutions. In this he is in agreement with those who recognize the
kind of necessity arising from primary intensions (Chalmers 2004) or
'*A* intensions' (Jackson 1998), such intensions
being determined by (some) phenomenal properties of the kinds referred
to.




Ayer also repudiated causal necessity. Following Hume, he
thought causation could be reduced to regularity: "*c*
causes *e*" is equivalent to "whenever *c*
then *e*". This latter proposition is then a law of
nature, which is just a generalization to which we have a certain
attitude. So contingent generalizations and laws of nature are much
the same; they differ only in that we rely on the latter more than the
former, and are prepared to treat the law as though it possessed some
stronger modality, though in fact it does not.




The lack of necessity attaching to causes made Ayer's acceptance of
human freedom undemanding. Having denied the existence of any causal
necessity it was open to Ayer to be a compatibilist: determinism could
be true (all action could be caused), but one could still accept that
this left it open as to whether the agent could have done otherwise,
given that the existence of the cause did not *necessitate* the
action. Ayer argued that the relevant contrast to freedom was not
causality, but constraint, or compulsion, which are a
'special' sort of cause. So if our actions could be caused
whilst not being 'constrained' in any way, then
determinism could be true and we could still be free. It was just as
well that this position was available, claimed Ayer, because being
held morally responsible for our actions required that these be not
the result of sheer chance.




This leaves, as Ayer recognized, a problem: if freedom is possible
because causes don't necessitate, then am I *ever* unfree?
Ayer's reply was straightforward. It is only some causes that deprive
us of freedom; if a robber puts a pistol to my head and demands my
money, he has left me without a reasonable alternative, so I am not
morally responsible for the action I am made to do. So to say that I
could have done otherwise is just to say that I would have done
otherwise had I so chosen, that my action was voluntary in the way in
which the kleptomaniac's isn't, and that nobody compelled me to
act in the way that I did. (See "Freedom and Necessity",
1954). This 'resolution' of the problem remains
unsatisfactory; Ayer's type of compatibilist does not have an
acceptable account of why it is that some causes are sufficient to
make my action not free, whilst others contain no such threat. As he
says, all causes are equally necessitating - none of them
necessitate, not even the 'special' sort of causes that,
he alleges, threaten our freedom.


## 7. Ethics




The emotivism espoused by Ayer in *LTL* was supported by his
belief in the distinction between fact and value. Given, he thought,
that there were no moral facts to be known, there could be no
verification of such facts, and so moral utterances could have no
cognitive significance. And given the connection between moral
'judgment' and motivation, and the connection between
motivation and feeling, it was natural to see moral utterances as
having the function of expressing our feelings, or
'emoting'. This view, Ayer was careful to point out, was
not that associated with subjectivism, that in making moral claims we
are *describing* our feelings. This latter view would make
moral claims truth-evaluable, and Ayer's moral emotivism denied that
they were so evaluable. So when we say: "Cruelty towards
children is wrong" we are really expressing a negative attitude
towards killing children, and when we say "Being kind to old
people is good" we are expressing positive feelings towards such
acts of kindness. The expression of such positive or negative
feelings, he later thought, also contained a prescriptive element, so
in such expressions we are also encouraging others to share those
feelings, and to act accordingly. As this makes clear, the attitudes
expressed were towards classes of acts, and not particular acts.




Emotivism was thought by some to be the *reductio ad absurdum*
of the verificationist theory of meaning, and indeed it was not the
preferred metaethical position of other positivists, some of whom
preferred a consequentialist approach, and so emotivism could be seen
as separable from verificationism. In fact, in the
"Introduction" to the second edition of *LTL* Ayer
stated that his commitment to emotivism would survive any demise of
his positivism, and it later became clear that it was because Ayer
thought moral judgments to be not fact-stating that he concluded they
were unverifiable (see "The Analysis of Moral Judgments"
in Ayer 1954). Emotivism was given additional support by
C.L.Stevenson, who had developed his ideas independently of Ayer, in
his book *Ethics and Language* (1944). In subsequent decades,
it spawned a family of what came to be called
"expressivist" views in metaethics, which sought to state
the view with a sensitivity to the logical problems Ayer's
formulation raised. 




It has been suggested (Dreier 2004) that Ayer faced a particular
difficulty in defending this brand of non-cognitivism; the combination
of affirming a redundancy theory of truth with the denial that moral
claims can be true looks suspicious. Although the two views are not
incompatible (Ayer denied that moral claims were assertions, and the
redundancy of the truth-predicate held only for assertions), the
tension between the two is symptomatic of the worry that moral claims
have so many of the features of truth-evaluable assertions that one
has to be unjustifiably revisionist in construing them as
non-meaningful. They are, after all, typically expressed in indicative
sentences, and people appear to dispute moral claims. This latter
point Ayer did respond to: moral disagreements were, he (and
Stevenson) claimed, either genuine disputes about non-moral facts, or
simply not genuine disagreements. (For an examination of the trouble
that moral disagreement makes for emotivism, see Smith 1986.) There
was, however, a further, more troubling, point about the role of moral
terms in arguments: moral terms can be used in arguments in which the
moral term appears in a conditional, and so is not there contributing
to the expressive force of the utterance, so not expressing any
emotion of the speaker. This latter point has been developed into a
line of reasoning (called the "Frege-Geach" problem)
against expressivism in general. The problem for the expressivist is
to make sense of simple arguments such as the following: (1) If John killed
Jane, he did something wrong. (2) John killed Jane. So (3) John did
something wrong. The argument appears to be valid, and so not to
involve any ambiguity, but the moral term can be construed as having
expressive force only in (3), not in (1). Expressivism, and so
emotivism, seems to introduce an unwarranted equivocation into the
argument.




It is perhaps these 'surface' features of moral discourse,
those that make it look like moral claims are assertions, and hence
expressions of belief, and so truth-evaluable, and that moral
disagreement appears to be genuine *moral* disagreement, that
later tempted Ayer to consider Mackie's 'error' theory of
moral language (Mackie 1977) as closer to the truth (in Ayer
1984). The details of emotivism tended to disappear from the
metaethical scene in the latter half of the twentieth century, but
its guiding thoughts have remained very much alive in the expressivism
of Blackburn 1984, 1998, and Gibbard 1990. (See Altham, 1979, for a
sympathetic defense of these guiding thoughts, and Schroeder, 2010,
for a thorough treatment of the development of expressivism, with
particular attention paid to subsequent attempts to tackle the Frege-Geach
problem.)