Popper was born in Vienna, where his father was a lawyer, writer, and social
reformer. He left home and school at the
age of sixteen and enrolled in the University. After a few years as a trainee cabinet-maker
and then as a social worker he studied to become a schoolteacher. While in Vienna he was in close touch with
some of the members of the 'Vienna
Circle' of logical positivists, though he was not a positivist himself. After the publication in 1934 of his Logik der Forschung (Logic of Scientific Discovery) he was invited to England, where he met
many of the leading philosophers
and lectured at the London School of
Economics. He was appointed to a senior
lectureship in philosophy at
Canterbury University College, New Zealand in 1937, and in 1945 he accepted a
readership at the L.S.E., becoming professor of logic and scientific method in
1949. He was knighted in 1965, and was
also elected a Fellow of the British Academy and made a Companion of Honour.
Logic of Scientific Discovery (1959 English edn); Conjectures and
Refutations, 3rd edn.] According to the 'traditional' view of scientific
method the scientist devises experiments to provide him with measured observations. He then formulates explanatory hypotheses and attempts to confirm them
by finding appropriate supporting evidence. It seems then that, while the scientific laws which this inductive
procedure give rise to may be highly probable, they are not certain. Most working scientists are presumably happy
enough with this view. However, Popper
argues that this account of methodology is erroneous and he proposes an
alternative. We can never conclusively
establish the truth of a general statement such as 'All swans are white'; there
will always be observations that have not yet been made. But we need only one disconfirming instance,
namely, 'This swan is black', which will be sufficient to falsify a scientific law. Scientific methodology thus involves falsification procedures and not confirming ones; and is
essentially deductive. (He therefore in
effect dismisses the so-called problem of induction) [LSD, ch. I,
6; ch. IV] [a]. He argues that what the scientist should do
is to set up general statements as 'conjectures' that can be refuted by
counter-instances or modified to take account of special circumstances [CR,
ch. 1]. Take, for example, the statement
that water boils at 100C at sea
level. From this a richer hypothesis
enables us to explain the connection between the boiling point of water and
atmospheric pressure, and this in turn can be subjected to further attempts at
refutation and modification.
The postulation of hypotheses in
general is for Popper an exercise of the critical imagination. To the extent that they have withstood
testing procedures they are said to be 'corroborated' and merge into theories, though they can never be established
conclusively. But Popper says that in the course of time and
through successive modifications theories may be said to correspond with
increasing approximation to the truth. He in fact uses the term 'verisimilitude', which he defines by reference to the 'content', that is, the set of logical consequences of a theory [CR, ch. 10, sec. 3; also Addenda 3]. And building on Tarski's semantic theory of truth [see CR, ch. 10, sec. 2; also Objective
Knowledge, ch. 9] (which Popper believes can be extended to natural languages) he argues in
favour of a theory of
objective truth and correspondence to facts [b]. A theory t2, he says, has greater verisimilitude than theory
t1, if the truth-content of t2 but not the
falsity-content is greater than that of t1, or if the
falsity-content of t1, but not its truth-content is greater than
that of t2. Popper
stresses that corroboration and verisimilitude are not to be understood in
terms of the probability that a
hypothesis or theory is true. Indeed
there is a problem in that probability statements seem not to admit of
refutation. He therefore modified the relative frequency
theory by introducing the notion of a 'condensation limit' as a limit of
frequencies within a finite class so that the deviations of future frequencies
from this 'limit' might be measurable. Later, however, he moved away from the statistical account to adopt an 'objective propensity' theory [c] which supposes probability statements to
be about the properties of experimental conditions. [See CR, ch. 1, Appendix.]
The emphasis on falsifiability as opposed
to verifiability is important not only because it lies at the heart of Popper's account
of scientific methodology but also because it provides him with what he calls the criterion of demarcation, which enables him to distinguish
genuine from pseudo-science.
[CR, ch. 11]. Consider the
statement 'It will rain sometime in the next million years'. This cannot be falsified, and is to all
intents and purposes certain; it has maximum probability. However, its
'information content' is virtually nil. This is to be contrasted with, say, 'Rain will fall on the London at 2
pm tomorrow'. This statement has a high
information content but is most improbable and is easily falsified. It is also, Popper says, the simplest. It is thus an appropriately scientific
statement. Highly probable
statements with low information content, which are accordingly
not falsifiable, are on the other hand not genuinely scientific, since nothing could ever count against them. Only hypotheses or theories which are open to rigorous testing
procedures are genuinely scientific. Metaphysical 'theories', Marxist 'laws', fundamental 'principles' of
Freudian psychoanalysis, and the like, although 'meaningful' are not scientific [d]. Popper rejects the verification principle of meaning [CR,
ch. 1, III] [e].
 It follows from Popper's account of
scientific procedure that he
does not accept the rationalist view that ultimate or complete knowledge of the
'essences' of things can be achieved [CR, ch. 3, sec. 3]. This is
not to deny the possibility of knowledge altogether; and Popper rejects 'instrumentalist'
theories of science [CR, ch. 3, secs 4 & 5], which consider
such entities as atoms, genes, and so on as merely convenient logical
constructions. 'Micro' objects, the supposedly theoretical
entities of science, can be regarded as real as physical objects given that
they are open to the same methodological testing procedures. It is not just a matter of convenience [a]. But he also rejects empiricist 'foundationalist' theories [CR, passim; especially Addenda 1],
which seek to ground knowledge in incontrovertible statements about supposedly
basic entitites such as sense-data or 'impressions'. This is because no observations can be 'pure' or 'bare'; we always bring
with us a framework of theory which guides us to the observations and has a
role to play in determining which 'facts' we should consider. Even in our earliest childhood we have
'expectations', albeit not consciously articulated (for example, that we are to
be fed). Such expectations, while psychologically or genetically
prior to observational experience and are thus in a sense the result of
'propensities', are not a priori valid and may be mistaken. Popper thus does not espouse a rationalist
innatist theory in any strict sense [b].
As we develop and become concerned
increasingly with problem-solving, particularly the problem of survival, our expectations are subjected
to critical testing so that errors which militate against survival may be
eliminated and new apparently successful modes of behaviour developed. This forms the basis of Popper's 'evolutionary'
epistemology [see Objective Knowledge] [c]. In the same way we come to
articulate our consciousness of the world through language, forming our
concepts in the light of our expectations; we come into contact with
abstractions, myths, customs, religions, and later on genuine science, all of
which are open to the critical procedure. These structures come to constitute what Popper calls 'World 3' the totality of our
inherited culture. They are
produced by 'World 2' (the world of minds) and are preserved in 'World 1'
(human brains, books, films, monuments, and so on) [see especially OK,
chs 3 & 4]. It is World 3 that constitutes objective knowledge in the strict sense [d]. Individual, private, subjective dispositions
or claims to know that something is the case are always contentious until they
have been subjected to testing, when they then pass, corroborated, into the
public and 'real' domain of World 3.
SOCIAL AND POLITICAL PHILOSOPHY
Knowledge.] Popper's theory of
objective knowledge incorporates his views on social, historical and political
issues which he developed earlier in his career. Scientific knowledge is clearly the product of an 'openness' to the
possibility that theories may have to be revised. This runs parallel to his view of the human
being as a free agent; the mind cannot be accounted for in causal deterministic
terms [a]. Likewise he rejects historicism [see The Poverty of
Historicism] whether the consequence of applying traditional and
incorrect scientific methodology to historical events, or of a supposedly special methodology appropriate uniquely to
history and also what he
supposed to be an associated social 'holism' which cannot be reduced to the behaviour of individuals. For
Popper the critical
falsificationist method, which characterizes genuine science, is applicable not
only to nature but also to human society, though in its individual or
particular aspects [b]. He is thus thoroughly critical of revolutions and wholesale
reconstructions of society. The ideal
pluralist democracy, to which he is committed, must therefore be a society
which is open to critical examination with a view to improvement through
minimizing suffering, unhappiness, and error [c]. [See The Open Society and its Enemies.] It must also be tolerant of different
views, though such tolerance cannot extend to those who would seek to undermine
free institutions even if the tyranny has the support of the majority. Similarly, rather than being concerned with
the traditional questions of political philosophy (who should rule the
wisest?, the best?, and so on), he places emphasis on the devising of
institutions that will minimize the risk of bad rulers.
Popper's philosophy is
wide-ranging and is characterized by energy and vision, combined with
analytical power. Popper rejected both
the 'foundationalism' proposed by some logical positivist philosophers and the
innate ideas of the rationalists. He
rejected also the assumptions of 'ordinary language' language
philosophy considering it to be vague and trivial. Understandably he was sympathetic to Russell and accepted
that the kind of analysis Russell advocated has a role to play in problem
solving. Not surprisingly, therefore,
Popper's influence has been felt more in political and social philosophy (and,
through Gombrich, in aesthetics) than in other areas of philosophy with the
exception perhaps of the philosophy of science. The key features of his thought may be summarized as follows.
(1) He rejected the verification principle and theory of meaning. He also stressed falsification of theories in
scientific methodology instead of verification.
(2) He used falsifiability as a criterion of demarcation for
distinguishing genuine science from what he regarded as spurious sciences such
as Marxism and Freudian psychoanalytical theory.
(3) He argued vigorously for openness of thought and for the 'open
society' rejecting authoritarianism and theories of historical inevitability.
(4) His distinction between three 'worlds', World 3 being 'objective'
knowledge, is an important feature in his later 'evolutionary epistemology'.
Many objections have
been made against his claims.
(1) It has been said that in his general account of scientific
explanation (a) he does not allow sufficiently for the possibility of anomalies
in experimental data; (b) he tends to concentrate on theories in isolation,
whereas, it has been claimed (by philosophers appealing to a 'holistic' view of
scientific methodology and knowledge acquisition), such theories cannot
adequately provide testable predictions; (c) his use of modus tollens arguments (p entails q; not-q; therefore not-p) could result in too ready a
rejection of theories; (d) he
underestimates the role that inductive procedures can play in scientific
methodology. It has also been suggested
(e) that science does not develop in the measured progressive 'evolutionary'
manner implied by his account: he should
have given more consideration to the way that paradigms are overturned.
(2) On the specific issue of falsification, it has been argued that
theories can always be protected from this by rejecting auxiliary hypotheses or
by changing one's assessment of probabilities. Indeed such moves may well be characteristic of scientific procedures,
contrary to Popper's claims. Moreover,
demarcation may not be as clear cut as Popper seems to suggest. Probability is never zero; the possibility
that a given claim can be falsified can never be ruled out.
(3) In his explanation of 'verisimilitude' Popper talks of the degree
of 'truth content' over 'falsity
content'. But is there a test or
criterion for truth content at all in a falsificationist theory? In so far as he accepts a theory only so long
as it has not been refuted, Popper (who, contentiously, interprets Tarski's
semantic theory of truth as one of correspondence) may yet be appealing to
purely pragmatic considerations. It is also unclear whether he is advocating an
ideal towards which practising scientists should aspire or is providing an
actual description of the scientists' modus operandi.
(4) Understandably his social and political philosophy has been
criticized by thinkers who have espoused historicist or inevitability
theories. This of course remains a
matter of ongoing debate. However, even some philosophers who are broadly
sympathetic to his position have questioned his interpretation of Plato and
Hegel as enemies of the open society [see 3d]. Whether this is a fair criticism is a matter
to be determined as much by Plato and Hegel scholars as by followers of Popper.
(5) The view that scientific method is applicable to both the natural
and the human sciences [compare Hempel] is, to say the least, questionable [see also Gadamer].
Popper: Die Logik der Forschung (1934) (The
Logic of Scientific Discovery,
author's trans. 1959); The Open Society and its Enemies (1943); The Poverty of Historicism, 2nd edn (1957); Conjectures and
Refutations: The Growth of Scientific
Knowledge (1963); Objective Knowledge: An Evolutionary Approach (1972).
B. Magee, Popper.
Burke, The Philosophy of Popper.
O'Hear, Karl Popper.
Currie. & A. Musgrave (eds), Popper and the Human Sciences. Nijhoff,
Schilpp (ed.), The Philosophy of Karl