He was born converted parents Juif S with the Protestantisme. He makes career like apprentice cabinetmaker.
Then he studied with the Université of Vienna and became teaching with the College in Mathématiques and Physique. It côtoya the Circle of Vienna (neopositivist), which made known it, but without never entering there. Its thought was influenced by its readings of Frege, Tarski and Carnap.
In 1936, it gave conferences in Great Britain, where it met its compatriots Hayek and Gombrich. In 1937, it accepted a proposal of lecturer ( lecturer ) with Christchurch in New Zealand, where it passed the war.
Beginning 1946, it returned to settle with London. On a proposal of Hayek, he became off professor with the London School Economics; he founded there in 1946 the department of Logique and Méthodologie of sciences (today Department off Philosophy, Logic and Scientific Method). He also took part in many seminars and conferences in other universities, in particular American.
He was member of the British Academy.
The problem of the demarcation
For Popper, the fundamental problems in Philosophie of sciences are that of the demarcation: it is the question of the distinction between what concerns science and what is “not-science”.
To include/understand this problem, it is initially necessary to wonder about the place of the induction in the scientific discovery: All sciences (*) are based on the Observation world. As this Observation is by partial nature, the only possible approach consists in drawing from the general laws of these Observation S (let us notice that it is the general and fundamental approach of any living organism which learns from its medium). If this step makes it possible to advance, it does not guarantee to in no case the accuracy of the conclusions. For Popper, it is thus necessary to take with serious the analysis Hume which shows disability attends induction.
(*): except for the Mathematical and Logique which are deductive constructions on axiomatic bases that they chooses arbitrairement. For example, a collection of Observation S (“ I see passing from the swans blancs ”) a general proposal logically (“  never makes it possible to induce; All the swans are blancs ”), because the only observation does not say anything the observations to come; there remains possible that only one contrary observation (“ I saw passing a swan noir ”) the invalid.
This criticism of induction thus leads Popper to call into question the idea (expensive with the positivists) of checking. Rather than speaking about “checking” of a Assumption, Popper will speak about “Corroboration”, i.e. of observation which goes in the direction envisaged by the theory. However, even by a great number of experiments, corroboration does not make it possible to conclude with the “truth” from a general assumption (presumedly valid for all the observations until the end of times).
A scientific proposal is thus not a checked proposal - nor even verifiable by the experiment -, but a refutable proposal (or falsifiable) which one cannot affirm that she will never be refuted. The proposal “God exists” for Popper is equipped with direction, but it is not scientist, because it is not refutable. The proposal “all the swans are white” is a scientific Conjecture. If I observe a black swan, this proposal will be refuted. It is thus the step of Conjecture S and Réfutation S which makes it possible to make grow the Connaissance S scientists.
In this step, the Théorie can thus precede the Observation.
He thus affirms to reject this method of the induction (being unaware of at the time the Théorème of Cox-Jaynes), and to substitute to him the Réfutabilité (English: falsifiability ). It is this principle which will be the criterion of demarcation.
It can be thus formulated: if one understands by simple statement a report/ratio of Observation, we can say that a theory is scientist if it is divided into two subclasses of basic statements:
- the class of the statements which contradict it, called potential falsifieurs (if these statements are true the theory is false);
- the class of the statements with which it agrees (if these statements are true, they corroborate it).
The criterion of falsificability of Popper is not distinguished in its principle from a test from falsificability bayésien, except the fact that he works only in discrete logic (false truth/) while the bayésiens vary the values of truth on a continuous beach of the interval] 0,1
Vocabulary: Conscious of the direction running of the falsifiable word (and its derivatives) in French, Karl Popper, in the foreword of one of its books (in French) request to use in the place to refute, refutation and its derivatives. (reference to be followed).
Limits of the field of application
Let us draw the attention to the fact that this criterion applies to theories (like Newtonian mechanics) and not to fields (like physics). It is generally considered that a field is a science if the corpus of the theories which are generally allowed there respects the criteria of Popper. Moreover, this scientific character or not, is of nothing an indicator scientific truth (since a theory is regarded as true only until its refutation), nor of the scientific interest: The history of sciences teaches that many scientific theories were born on a compost which did not respect the current criteria for a science.
The nonscientific character of a theory is often regarded as synonym of “ without interest scientifique ”, which would imply that science is only worried what is scientist , whereas science tries to codify, precisely, which is not it (for example, to see Histoire of sciences). This ends up serving epistemology and causing the rejection of this theory by the defenders of the attacked fields.
According to this criterion, the Astrology (that it is included/understood as a theory or a theoretical field), the Métaphysique or the Psychanalyse (therapeutic method) do not raise of the Science, since one can draw no testable predictive statement from it and that consequently no experiment makes it possible to establish (or not) the refutation of it - and thus a confirmation either (see the vintage and cooks it). In practice however, it is not always easy to refute a theory which fails to explain an experimental fact, in particular if one does not have a better theory. In certain cases, two contradictory theories can cohabit, because one and the other are supported by certain facts and are contradicted by others. The Physique, which is however the typical example of a science controlled by the epistemology according to Popper, gives us an good example, with the enigma of the Précession of the main roads of the Mercury orbit that the Newtonian Mécanique did not manage to explain, and who was solved by the theory of the General relativity, it even entering then in conflict with some of the experiments which support the quantum Mécanique. Let us recall it: no real scientific step, out mathematics and logic, is possible without the induction, which underlined Bertrand Russell.
The case of the Social sciences
The criteria of scientificity of Popper pose problem in the social sciences, where they are difficult even impossible to apply. Indeed:
- the Expérimentation controlled there is most of the time impossible, in particular in social sciences;
- the comparison of situations observed is not convincing because it is impossible to be sure that all the conditions are the same ones;
- it is impossible to separate the effects of the various causes which intervene in the situations observed.
It results from it that the criterion of Réfutabilité is operational only in the applied sciences or of Observation. This position is that of the methodological dualism, according to which the methods applicable to sciences of nature on the one hand, with the social sciences on the other hand, are different. It is one of the bases of the Austrian École of economy.
Popper however defended the opposite position, that of the unicity of the scientific model. In a famous controversy with Theodor Adorno, it defends even the Sociologie like social science being able to subject itself to the falsifiability. The whole of this debate is summarized in a work which it codirigé with Adorno: From Vienna to Frankfurt. The quarrel of Social sciences , 1979 (see inside this work the conference of Popper: the logic of social sciences , and the answer of Adorno On the logic of social sciences ).
To the extreme and, this problem gives place to controversies around fields such as the Psychanalyse or the Homéopathie and even the Astrologie. If these three fields offer neither reliable experimental evidence today, nor criteria of refutability, it can be completely excluded only the technological change and/or the development future scientists change this state of the things. Despite everything, this statute of “ non-scientifique ” led a part (more or less important according to the accused field) of the scientific community to reject these fields like charlatanism, especially if, as it is the case for astrology, the available data contradict the theses of holding of the astrology (cf the famous effect which March forever shown in a convincing way).
The criticism of the Historicisme: a vision indeterminist of the world
The two works openly political of Popper are Misère of the historicism and the open Company and its enemies , written both under effort of war during the Second world war. They have as a focal point the criticism of the Historicisme and the political theories which result from this.
In the foreword with the French edition (Plon, 1955) of Misère of the historicisme, Karl Popper explains:
That it is enough for me to say that I understand by a theory, concerning all social sciences, which makes historical prediction their principal goal, and which teaches that this goal can be reached if one discovers the “rates/rhythms” or the “reasons” ( patterns ), the “laws”, or the “general tendencies” which underlie the historical developments.
The node of its argumentation is the strictly logical proof that it is impossible to determine the future. (Throughout its career, Popper attempted to prove the Indéterminisme.) Therefore, all the theories being based on a Prophecy or an alleged course of the history are invalid. He thus particularly criticizes the Marxisme which brings back all the history to inescapable the Class struggle.
What was initially to constitute notes on Misère of the historicism takes consistency gradually and becomes the open Company and its enemies . In this work, Karl Popper shows how the Historicisme led to the Totalitarisme S. Plus particularly, it attempts to boldly criticize - thanks to a deep knowledge of the texts - three recognized philosophers: Plato, Hegel and Karl Marx. It reproaches them the fundamental error for setting up philosophical systems historicists, centered on a natural law of evolution of the world: decline of the real things at Plato, the development of the Spirit at Hegel and the class struggle at Marx.
To the system historicist, Popper opposes a philosophy primarily founded on the Indéterminisme. This design follows that of sound epistemology, according to which knowledge progresses by test/error ( trial and error ): to solve a given problem, one proposes several assumptions/solutions which it is a question of testing and one eliminates those which lead to an error. Popper draws from this design a political position: as it is impossible to predict the course of the history, it is necessary to progress gradually by test/error, from where a “fragmentary” design of the Social sciences ( piecemeal social engineering ) in which nothing is played in advance. Instead of envisaging an overall plan to reorganize the company, it acts contrary to proceeding by small keys, in order to be able to include/understand the effect of such or such measurement, and to correct the inevitable unexpected consequences of them.
The work of Popper is not limited to epistemology. Even if he always refused to be presented in the form of a political philosopher, it does not remain about it less than it was delayed much on the policy and in particular on the operation of the democracy.
A vision liberal policy
The political ideas of Popper are thus basically liberal, as its participation in the foundation testifies some to the Société of the Mount Pilgrim at the side of very committed liberals like Ludwig von Mises, Milton Friedman and Friedrich Hayek. Popper indeed proposes a vision of the world in which the freedom of the man is fundamental and must be protected. In particular, in its critic of the Marxism and the historicism hégélien, it fights a design of the world in which the man is impotent vis-a-vis the walk of the history. Popper supports on the contrary that the ideas influence the world and the history, and that the man, and in particular the philosophers, have important a responsibility .
The liberalism of Popper does not bar from the intervention from the State, including in the economic domain. On the contrary, it makes of it a condition of the exercise of freedoms of the individuals, because of the paradox of freedom :
Freedom, if it unlimited, is led with its opposite; because if it is not protected and is not restricted by the law, freedom necessarily leads to the tyranny of most extremely on weakest.
Also the State has the duty to limit freedom so that no individual must have to be alienated with another:
This is why we require that the Absolute limit freedom to a certain extent, so that the freedom of each one is protected by the law. Nobody must be at mercy others, but all must have the right to be protected by the State. I believe that these considerations, initially aiming the field of the rough force and the physical intimidation, must also be applied to the economic domain. We must build social institutions, imposed by the State, to protect the lower-income group from economically strong.
Theory of the democracy
Popper distinguishes only two types of political regimes: the democracy and tyranny. As to its practice, Popper does not allot more importance than one should not any for the words; one should include/understand by these two terms only terminological reference marks. Thus, it is not by the etymology that Popper will define the democracy, which would be then the " government of the peuple".
The traditional question since Plato " who owes gouverner" is rejected by Popper as being essentialist. With this problem, he proposes to substitute some more realistic: " do there exist the shapes of government that it is necessary for us to reject for reasons morals? And conversely: do there exist the shapes of government which enable us to get rid of a government…? "
Will be thus described as democratic a mode in which the leaders can be relieved by directed without bloodshed. Any other government in which the dismissal of the leaders cannot pass that by violence could be qualified of tyrannical .
The problem to which Popper will stick will be then to think the organization of the democracy so that this one allow the dismissal of the leaders as well as possible. This is why Popper rejects without call the direct democracy and the poll proportional. Indeed, with the direct democracy, the people are responsible in front of itself, which is a contradiction: the people cannot relieve itself. With the poll proportional, the majority of the parties are necessarily represented in the assemblies in a more or less great proportion though it arrives at the time of the elections, and the majority parties then are often forced to have to control with them by creating coalitions, which means in light that certain parties could always take part in the capacity and never not to be relieved.
This is why the preference of Popper goes to democratic representative with majority poll, and this for null another reason that the weaknesses of the direct democracy and the poll proportional. Moreover, it seems to mark a clear preference for the two-party system, where the party opposing to the responsibility of criticize the assumptions formulated by the majority party, and conversely. The system of the internal primary educations to the parties makes it possible to add a self-criticism of the assumptions inside even parties.
Popper and the theory of the evolution
According to Popper, the selection of the scientific assumptions would concern a natural selection identical to that governing the evolution of the species (see Charles Darwin). Theory of the life and theory of knowledge would answer thus of the same process of progression per test and elimination of the error (a position rather close to that of Erwin Schrödinger). This is why one speaks about evolutionary epistemology.
By showing the analogies existing between the evolution of the species and the development of the scientific knowledge, Popper “ naturalize ” by doing this basic principles of its epistemology:
1. The rejection of induction : According to Popper, “ the theory comes before the facts ”: the assumptions precede and direct the observation. In the same way, when they vary the living organisms create new theories on the world, of new assumptions, that Popper names “ attentes ” and which is assimilated to the scientific theories: only those will be retained which correspond to a reality of the environment, those which the experiment, confrontation in the medium does not refute. For example, by increasing their rate of travel and their reactivity vis-a-vis the danger, the antelopes have “ théorisé ” need for being able to flee quickly, in particular to escape their predatory. Schematically, the antelopes current thus go down from those which, in the past, knew to run rather quickly to escape the lions. They of course did not do it in a conscious way (see Konrad Lorenz and the Imprégnation). It is through the hereditary modifications, the genetic Mutations, that living it “ essaie ” various adaptations to the environment, different “ solutions ” - which generates in their turn of new problems, in a race with the improvement that Popper explains in particular through the assumption of a genetic dualism .
2. The elimination of the error: Natural selection darwinienne and natural selection of the assumptions are identical insofar as both lead to the elimination of the error. The only difference residing between Albert Einstein and a Amibe is thus, according to Popper, that first is capable of “ extérioriser ” its error through the language, while second is condemned to disappear with it. A miscalculation will not cost the life Einstein. An error of adaptation for the ameba, if.
3. The solution to problem: While proceeding by elimination of the error, the scientific step, just like the evolution, make it possible to solve problems which, most of the time, appear completely clearly only once solved. In the case of the alive species, for example of the ameba, these problems must be “ objectifs ” since the latter is not conscious. The resolution of these problems carry out to levels of knowledge and of evolution superiors - with regard to biology to the emergence of “ forms of life more hautes ”.
Thus, while being based on a series of analogies perhaps aiming at founding the falsificationism ontologiquement, Popper estimates that “ the science ” is a biological activity, in what she answers a selection process natural.
This diagram of natural selection is articulated in three times. That is to say:
- P1: Initial problem;
- TS: Test of solution ( attempt solution in English);
- EE: Elimination of the error;
- P2: New problem.
An initial problem brings the production of assumptions aiming at solving it (of P1 with TS). These assumptions are tested by the means of the scientific experimentation (of TS with EE). Lastly, the resolution of the P1 problem involves the emergence of a new P2 problem. The logic of science just like that of the life answer, according to Popper, of this four-line diagram.
Concerning the epistemological statute of the theory darwinienne:
Popper supported that the Théorie of the evolution darwinienne by natural selection was not a true science, because irrefutable and Tautologique. It qualified it thus “ research program métaphysique ”, which caused some polemical, sometimes very sharp. The creationnists in particular tried to use the theses poppériennes to discredit the theory of the evolution. The philosopher ends up rectifying these interpretations in a letter addressed to the scientific magazine The New Scientist . Ultimement, it recognized with the theory of the natural selection the true statute of science: it estimated it inter alia able to explain the multiple processes of “ causation to the bottom ”. A position that its own evolutionary metaphysics could only reinforce.
Contrary to the neo-positivists of the Circle of Vienna, Popper does not oppose science to the Métaphysique. It worked out itself a metaphysics mixing Réalisme, Indéterminisme and evolutionism.
In the middle of this metaphysics poppérienne, one finds “ the theory of Worlds 1,2 and 3 ”:
- the “ World 1 ” is that of the physicochemical phenomena. By “World 1”, I understand what, usually, is called the world of physics, the stones, the trees and the physical fields of the forces. I intend to include also there the worlds of chemistry and biology .
- the “ World 2 ” is that of the conscience, of the primarily subjective psychic activity. By “World 2” I understand the psychological world, which usually, is studied by the psychologists of animals as well as by those which deal with the men, i.e. the world of the feelings, fear and the hope, the provisions to be acted and all kinds of subjective experiments, including the subconscious and unconscious experiments.
Four functions of the language
To the three functions of the language distinguished by its former professor Viennese Karl Bühler, Popper adds a fourth of it: the argumentative function. These 4 functions are the following ones:
- the expressive or symptomatic function , where the animal expresses an emotion, for example a cry of pain;
- the function of signal , by which the animal transmits a message, for example by a cry of alarm;
- the function of description , by which the gifted being of articulated language can describe with others something, for example time that it makes;
- the function of argued discussion , which makes it possible the man to rationally discuss by exerting its critical faculties, in “ argumentant ”, for example when one discusses of a philosophical problem.
With the development of these functions of the language the emergence of different “the   is correlated; Mondes ” poppériens. In particular, the “ World 3 ” appears with the fourth function of the language, and develops starting from the third.
Just like for the “ Worlds 1,2 and 3 ”, Popper estimates that the four functions of the language exert the ones on the others a “ control plastique ”.
The néo-Cartesian dualism of Karl Popper
By Analogy, Popper affirms capacity to solve the main issue of the Philosophie of the spirit, that of the relation body/heart. The heart would exert a “ control plastique ” on the body: for example, when I am held upright, the muscles of my legs are agitated the negligible ones and undetectable muscular movements aiming at ensuring stability. The heart corrects the balance of the body by eliminating the nonsuitable movements: she exerts on him a “ flexible control or plastique ”.
Thus, Popper was posed as a defender of the dualism and more precisely of the Interactionnisme. It estimated moreover that the assumption of Rene Descartes according to which the place of this interaction would be in the épiphyse (or pineal Body) is not so inept and improbable that the posterior generations wanted it to let believe.
two fundamental problems of the theory of knowledge (original title: Die beiden Grundprobleme der Erkenntnistheorie , 1930 - 1933). Note of the editor, Hermann: Far from being a simple draft - quite to the contrary, since “ celebrates it logical scientific discovery ” was in the beginning only one summary -, this first formulation of the falsificationnism poppérien anticipates certain ideas which will only reappear well later.
- Logical of the scientific discovery (original title: Logik der Forschung , Logic of research; The Logic off Scientific Discovery , 1934)
- Misery of the historicism ( The Poverty off Historicism , 1944 - 1945)
- the open company and its enemies ( Open The Society and Its Enemy , 1945)
- Conjectures and refutations ( Conjectures and Refutations: The Growth off Scientific Knowledge , 1953)
- knowledge objectifies ( Objective Knowledge: Year Evolutionary Approach , 1972)
- the unfinished search ( Unended Quest; Year Intellectual Autobiography , 1976)
- Television, a danger to the democracy (1995)
- the Lesson of this century , (1993)
- has Note one Verisimilitude
- The Self and Its Brain: Year Argument for Interactionism , (1977) with the neurophysiologist [[John Carew Eccles]].
- Open The Universe: Year Argument for Indeterminism , (1982)
- Realism and the Aim off Science , (1982)
- The Myth off the Framework: In Defense off Science and Rationality , (1994)
- Knowledge and the Mind-Body Problem: In Defense off Interactionism , (1994)
- Any life is solution to problem , 2 volumes, (1997).
- a universe of propensities: two studies on causality , (1992).
“a theory which is not refutable by any event which can be conceived is deprived of scientific nature. ” (Conjectures and réfutations, ch.1, section 1)
“the success of Hegel marked the beginning of “the age of the dishonesty” (as Schopenhauer described the period of the German idealism) and of “the age of irresponsibility” (like K. Heiden qualified the age of modern totalitarianism); of an initially intellectual irresponsibility then, it was one of its consequences, a moral irresponsibility; of a new age governed by the magic of the bright words and the capacity of the jargon. ” (La open company and its ennemis, ch.12)
“Liberalism and intervention of the State are not contradictory; no freedom is possible if the State does not guarantee it. ” in the open Company and its enemies (1962)
“This wave and intangible entity which one calls public opinion reveals sometimes a clearness without sophistication or, more usually, a moral sensitivity higher than that of the government in place. Nevertheless, it represents a danger to freedom if it is not limited by a strong liberal tradition. As a referee of the taste, it is dangerous; as a referee of the truth, it is unacceptable. ” (Conjectures and réfutations, ch.17, section 8)
“the intellectuals do not know anything” will say it to 83 years in its conference of Zurich the research of peace (Toute life is resolution of problème). More than one provocation it is a symbol of the relativity of the knowledge, and sterility of the conflict of doctrines.
“If one wonders why Popper, after so a long time and being as systematically ignored by philosophy and epistemology contemporary Frenchwomen, has profited for a few years from a real success from mode, it is to be feared as the answer must be sought not in a sudden and unhoped-for conversion so that it calls “critical realism”, but rather by the fact that, after several decades of philosophical and political dogmatism unrestrained, it gives to the French intellectual mediums the opportunity to cheaply offer a cure of undifferentiated and radical skepticism, which is not likely to endanger the fundamentally irrationalist convictions which continue to reign there” (Jacques Bouveresse, Popper article, Encyclopædia Universalis).
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