Category Archive: .Popper, Karl

Scientific methodology (German edition)

3. Die deduktive Überprüfung der Theorien. Die Methode der kritischen Nachprüfung, der Auslese der Theorien, ist nach unserer Auffassung immer die folgende: Aus der vorläufig unbegründeten Antizipation, dem Einfall, der Hypothese, dem theoretischen System, werden auf logisch-deduktivem Weg Folgerungen abgeleitet; diese werden untereinander und mit anderen Sätzen verglichen, indem man feststellt, welche logischen Beziehungen (z. B. Äquivalenz, Ableitbarkeit, Vereinbarkeit, Widerspruch) zwischen ihnen bestehen.

Dabei lassen sich insbesondere vier Richtungen unterscheiden, nach denen die Prüfung durchgeführt wird: der logische Vergleich der Folgerungen untereinander, durch den das System auf seine innere Widerspruchslosigkeit hin zu unter­suchen ist; eine Untersuchung der logischen Form der Theorie mit dem Ziel, festzustellen, ob es den Charakter einer empirisch-wissenschaftlichen Theorie hat, also z. B. nicht tautologisch ist; der Vergleich mit anderen Theorien, um unter anderem festzustellen, ob die zu prüfende Theorie, falls sie sich in den verschiedenen Prüfungen bewähren sollte, als wissenschaftlicher Fortschritt zu bewerten wäre; schließlich die Prüfung durch „empirische Anwendung“ der abgeleiteten Folgerungen.

Diese letzte Prüfung soll feststellen, ob sich das Neue, das die Theorie behauptet, auch praktisch bewährt, etwa in wis­senschaftlichen Experimenten oder in der technisch-praktischen Anwendung. Auch hier ist das Prüfungsverfahren ein deduktives: Aus dem System werden (unter Verwendung bereits anerkannter Sätze) empirisch moglichst leicht nach­prüf­bare bzw. anwendbare singuläre Folgerungen („Prognosen“) deduziert und aus diesen insbesondere jene ausgewählt, die aus bekannten Systemen nicht ableitbar sind, bzw. mit ihnen in Widerspruch stehen. Über diese – und andere – Folgerungen wird nun im Zusammenhang mit der praktischen Anwendung, den Experimenten usw. entschieden. Fällt die Entscheidung positiv aus, werden die singulären Folgerungen anerkannt, verifiziert, so hat das System die Prüfung vorläufig bestanden; wir haben keinen Anlaß, es zu verwerfen. Fällt eine Entscheidung negativ aus, werden Folgerungen falsifiziert, so trifft ihre Falsifikation auch das System, aus dem sie deduziert wurden.

Die positive Entscheidung kann das System immer nur vorläufig stützen; es kann durch spätere negative Entscheidungen immer wieder umgestoßen werden. Solang ein System eingehenden und strengen deduktiven Nachprüfungen standhält und durch die fortschreitende Entwicklung der Wissenschaft nicht überholt wird, sagen wir, daß es sich bewährt.

Induktionslogische Elemente treten in dem hier skizzierten Verfahren nicht auf; niemals schließen wir von der Geltung der singulären Satze auf die der Theorien. Auch durch ihre verifizierten Folgerungen können Theorien niemals als „wahr“ oder auch nur als „wahrscheinlich“ erwiesen werden.

The problem of the growth of knowledge

The central problem of epistemology has always been and still is the problem of the growth of knowledge. And the growth of knowledge can be studied best by studying the growth of scientific knowledge.

And yet, I am quite ready to admit that there is a method which might be described as ‘the one method of philosophy’. But it is not characteristic of philosophy alone; it is, rather, the one method of all rational discussion, and therefore of the natural sciences as well as of philosophy. The method I have in mind is that of stating one’s problem clearly and of examining its various proposed solutions critically. [Preface, 1959]

The problem of the growth of knowledge (2)

Thus I see the problem of knowledge in a different way from that of my predecessors. Security and justification of claims to knowledge are not my problem. Instead, my problem is the growth of knowledge: in which sense can we speak of the growth or the progress of knowledge, and how can we achieve it? [37]

Vague induction

It is clear that, if one uses the word “induction” widely and vaguely enough, any tentative acceptance of the result of any investigation can be called “induction”. In that sense, but (I must emphasize) in no other, Professor Putnam is quite right to detect an “inductivist quaver” in one of the passages he quotes (section 3). But in general he has not read, or if read not understood, what I have written … . [994]

Infinite learning

Thus every statement (or ‘basic statement’) remains essentially conjectural; but it is a conjecture which can be easily tested. These tests, in their turn, involve new conjectural and testable statements, and so on, ad infinitum; and should we try to establish anything with our tests, we should be involved in an infinite regress. But as I explained in my Logic of Scientific Discovery (especially section 29), we do not establish anything by this procedure: we do not wish to ‘justify’ the ‘acceptance’ of anything, we only test our theories critically, in order to see whether or not we can bring a case against them. [521]

Severely risky

A serious empirical test always consists in the attempt to find a refutation, a counterexample. In the search for a counterexample, we have to use our background knowledge; for we always try to refute first the most risky predictions, the ‘most unlikely … consequences’ (as Peirce already saw); which means that we always look in the most probable kinds of places for the most probable kinds of counterexamples—most probable in the sense that we should expect to find them in the light of our background knowledge. Now if a theory stands up to many such tests, then, owing to the incorporation of the results of our tests into our background knowledge, there may be, after a time, no places left where (in the light of our new background knowledge) counter examples can with a high probability be expected to occur. But this means that the degree of severity of our test declines. This is also the reason why an often repeated test will no longer be considered as significant or as severe: there is something like a law of diminishing returns from repeated tests (as opposed to tests which, in the light of our background knowledge, are of a new kind, and which therefore may still be felt to be significant). These are facts which are inherent in the knowledge-situation; and they have often been described—especially by John Maynard Keynes and by Ernest Nagel—as difficult to explain by an inductivist theory of science. But for us it is all very easy. And we can even explain, by a similar analysis of the knowledge-situation, why the empirical character of a very successful theory always grows stale, after a time. We may then feel (as Poincaré did with respect to Newton’s theory) that the theory is nothing but a set of implicit definitions or conventions—until we progress again and, by refuting it, incidentally re-establish its lost empirical character. (De mortuis nil nisi bene: once a theory is refuted, its empirical character is secure and shines without blemish.) [325-6]

A whiff of Pangloss

Democracies have serious drawbacks. They certainly are not better than they ought to be. But corruption can occur under any kind of government. And I think that every serious student of history will agree, upon consideration, that our Western democracies are not only the most prosperous societies in history – that is important, but not so very important – but the freest, the most tolerant, and the least repressive large societies of which we have historical knowledge.

I have said this before, of course. It would be almost criminal not to say it if one believes it. One must fight those who make so many young people unhappy by telling them that we live in a terrible world, in a kind of capitalist hell. The truth is that we live in a wonderful world, in a beautiful world, and in an astonishingly free and open society. Of course it is fashionable, it is expected, and it is almost demanded from a Western intellectual to say the opposite, to lament loudly about the world we live in, about our social ills, about the inherent injustice of our society, and especially about the alleged terrible inequalities, and the impending day of reckoning.

I do not think that any of this is true. It is true that there are a people who are very rich. But what does it matter to me or to you? It is most certainly not true that anybody suffers because a few are very rich, not to mention that quite a few of the few who are rich spend much of their money on such things as founding universities and lectureships and on scholarships and cancer research.

The truth is that Western democracies are the only societies in which there is much freedom, much welfare, and much equality before the law. Of course, our society is very far from perfect. There is much misuse of drugs, of tobacco, and of alcohol. [335]

A party in the interest of all

And so it becomes clear that the political aims of us all must be the containment of power rather than its attainment; the control of and resistance to power rather than its use for some ideological purpose. My very simple and hopeful proposal is this: At least one of the major politcal parties in a state should declare its interest in trying to surmount the dominance of ideologies, and its readiness to try to replace them by a straightforward programme of serving the most urgent needs of all. [390]

Bold piecemeal engineering

I do not suggest that piecemeal engineering cannot be bold, or that it must be confined to ‘smallish’ problems. But I think that the degree of complication which we can tackle is governed by the degree of our experience gained in con­scious and systematic piecemeal engineering. [ch. 9, n3]

The scope of piecemeal engineering

The difference between Utopian and piecemeal engineering turns out, in practice, to be a difference not so much in scale and scope as in caution and in preparedness for unavoidable surprises. … [W]hile the piecemeal engineer can attack his problem with an open mind as to the scope of the reform, the holist cannot do this; for he has decided before­hand that a complete reconstruction is possible and necessary. [63]

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