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Compiled by Anthony Harrison-Barbet


POPPER

(1902 — 1994)

 

CRITICAL EMPIRICISM

Karl 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.

 

METHODOLOGY

[1] [The 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].

 

KNOWLEDGE

[2] 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

[3] [Objective 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.

 

CRITICAL SUMMARY

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].

 

READING

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).

Studies:

Introductory

B. Magee, Popper.

Advanced

T. E. Burke, The Philosophy of Popper.

A. O'Hear, Karl Popper.

Collections of essays

G. Currie. & A. Musgrave (eds), Popper and the Human Sciences. Nijhoff, Dordrecht, 1985

P. A. Schilpp (ed.), The Philosophy of Karl Popper.

 

 

CONNECTIONS

Popper

 

[1a] Scientific methodology: falsification not verification; deductive so avoids problem of induction

   Hume

   Peirce

   Schlick

Carnap

   Hempel

Quine

Ayer

[2b]

[2c]

[1b]

[4c 5b]

[2b]

[3a]

[4d]

 

[1b; cf. 2c]. Modification of theories → 'verisimilitude' (logical consequences of theory as test) — semantic theory of truth & correspondence to facts

   Carneades

   Posidonius

   Cicero*

   Nicholas of Cusa

   Peirce

   Davidson

[2b]

[2c]

[1c]

[1b]

[2a c]

[1a]

       [*Popper attributes the term 'verisimilitude' to
   Cicero, for whom he says it was synonymous
   with ' probability' (CR, p 404, n. 6)]

 

[1c] Corroboration and verisimilitude not understood in terms of probability that hypothesis is true; relative frequency and objective propensity theories

   Carneades

   Cicero

Carnap

Ayer

[2b]

[1c]

[5a]

[4d]

 

[1d] Pseudo-science and criterion of demarcation; hypotheses genuinely scientific if open to testing; metaphysics not 'meaningless'

   Marx

Carnap

[esp. sec. 2]

[1b]

 

[1e] Rejection of verification theory of meaning

   Schlick

   Carnap

[2d]

[1a 3a]

 

[2a] Rejection of (i) rationalists' knowledge of essences, (ii) instrumentalism in science; 'reality' of theoretical entities — not a matter of convenience

   Descartes

   [through Galileo/Newton]

   Berkeley

   Carnap

Hempel

 

[2b]

   

[4b]

[3d 4c]

[1c]

 

 

[2b] Rejection of foundationalism; no 'pure' observation; presupposed framework of expectations (innate propensity but not a priori rationalistic)

   Hume

   Kant

   Wittgenstein

Carnap

Habermas

[1c]

[2c]

[2g]

[4c]

[2b]

 

[2c; cf. 1b] 'Evolutionary epistemology' and critical testing of expectations (non-dialectical progress)    Hegel [1c]

 

[2d] 'World 3' — totality of inherited culture: objective knowledge; realism    Putnam

[1g]

 

[3a] Scientific knowledge and 'openness'; human beings as free agents — rejection of causal determinism, historicism, and social 'holism'

   Hegel

   Comte

   Marx

   Dilthey

Quine

[7d 9a]

[1a 2e]

[2a]

[3a]

[3a]

 

[3b] Falsification method applicable to both natural and human sciences

Carnap

   Hempel

[4b]

[2a c]

 

[3c] Critique of revolutionary/ reconstructionist views of human society; advocates pluralist democracy and minimizing error and misery

   Plato

   Hegel

   Marx

   Ortega y Gasset

[sec. 14]

[7d CSa]

[2e]

[3c]