Mauro Murzi's pages on Philosophy of Science - Logical Positivism
Influences on European Philosophy
 The American Period Michael Friedman’s Analysis of Logical Positivism

# [3. History of Logical Positivism.]

## d. Influences on European Philosophy.

Some of the relations between logical positivism and Polish philosophy have already mentioned above. In the twentieth century, Polish philosophers were very interested in logical problems. Their works contributed to the development of several branches of logic, such as semantics and many-valued logic. Polish logicians analyzed logical aspects of logical positivist philosophy. Marian Przelecki's work The Logic of Empirical Theories, 1969, is a good example of such studies. In her work, Przelecki examined the logical structure of theories and proposed a semantic model of a formalized language suitable for a scientific theory. She used a relatively simple extension of Tarskian classical semantics. In her theory not all statements are true or false: a proposition can be indeterminate, that is, neither true nor false (but the law of the Excluded Middle is always true). Therefore, there is at least a statement, say P, so that (i) P is not true, (ii) P is not false, and (iii) Pv¬P is true. A very interesting property of Przelecki's semantics is the following one: let Ax be the set of axioms of a scientific theory and suppose that Ax is finite, and let A be the conjunction of all statements in Ax. It is possible that A is false even if each statement in Ax is not false (that is, the conjunction of a finite number of assertions can be false even if every assertion is not false). This property is very useful in explaining a well-known situation: when a theory is proved false it is often very difficult to determine the wrong axiom. Another outcome of Przelecki's theory is a semantic characterization of the rules of correspondence. It was proved that the Carnap sentence is the weakest rule of correspondence, but it is not the only possible one. For example, suppose the following two statements are the axioms in Ax:

1. (x)(O1x → T1x)
2. (x)(O2x → ¬T1x)

The observational terms are O1, O2, and the only theoretical term is T1. Every one of the following statements is an admissible rule of correspondence:

1. (x)[(O1xv O2x) → (T1x ←→ O1x)]
2. (x)[¬(O1x & O2x) →((O1x v O2x) → (T1x ←→ O1x))]
3. (x)¬(O1x & O2x) → (x)[(O1x v O2x) → (T1x ←→ O1x)]

The last statement is logically equivalent to the Carnap sentence.

The English philosopher Alfred Jules Ayer (1910-1989) played an important role in spreading logical positivism. His work Language, Truth and Logic, 1936, was an immediate success. In that book, Ayer completely accepted both the Verifiability Principle and the distinction between analytic and synthetic statements, and so he asserted that metaphysical sentences are meaningless. A direct influence was exerted by Waismann and Neurath who immigrated to England in 1937 and 1940 respectively. Waismann taught at Cambridge and, from 1939 to 1959, at Oxford, where he taught philosophy of mathematics and philosophy of science. During this period Waismann was very interested in the philosophy of Wittgenstein.

Relations between Italian philosophy and logical positivism developed in the early stages of logical positivism. The Italian mathematician and philosopher of science Federigo Enriques (1871-1946) took part in the congresses on scientific philosophy and collaborated on the International Encyclopedia, and Neurath and Carnap contributed articles to the journal Scientia edited by Enriques. In 1934, Ludovico Geymonat (1908-1991) published a work on logical positivism: La Nuova Filosofia della Natura in Germania. Geymonat had the opportunity to study with Schlick, Reichenbach, Carnap, and Waismann. He later held the first chair in Italy of philosophy of science (1956). However, the interest of Italian philosophy in logical positivism was primarily directed towards historical research. Francesco Barone distinguished himself with his work Il Neopositivismo Logico, 1953, a detailed and up-to-date historical and philosophical analysis of logical positivism, which deserves mention because it focused attention not only on the Vienna Circle but also on the American period of logical positivism and on some forgotten philosophers (even now it is not impossible to find valuable dictionaries of philosophy that identify logical positivism with the Vienna Circle).

French philosophy was marginally interested in logical positivism. Charles E. Vouillemin translated several logical positivist works and, in 1935, published La Logique de la Science et l'ecole de Vienne, a book in which he examined the philosophy of the Vienna Circle. Luis Rougier (1889-1982) gave reports about logical positivism ("Une Philosophie Nouvelle: l'empirisme Logique" in Reveu de Paris, 63, 1935), collaborated on the International Encyclopedia of Unified Science and contributed works to Erkenntnis.

Scandinavian philosophers also expressed interest in logical positivism. Finnish Eino Kaila (1890-1958) employed for the first time the expression "Logical Neo-positivism" for denoting the new philosophical movements (E. Kaila, "Der Logistische Neupositivismus" in Annales Universitatis Aboensis, ser. B, 13, 1930). Kaila published in 1939 a work that used the principles of logical positivism (The Human Knowledge, in Finnish). He taught philosophy at the University of Helsinki. Among his students was George Henrik von Wright (1916-2003) who published a study about logical positivism (Logical Empiricism: A Principal Movement in Modern Philosophy, 1943, in Swedish, and 1945, in Finnish). Wright contributed to the development of both modal and deontic logic. Swedish philosopher Ake Petzäll (1901-1957) was mainly influenced by the Vienna Circle and in 1930-31 he went to Vienna, where he took part in the Vienna Circle meetings. In 1931 he wrote Der Logistische Neupositivismus. In 1935, he founded a new journal, Theoria, published in Göteborg. It was the journal in which Hempel published his very first description of the paradoxes of confirmation ("Le Problème de la Vérité", 3, 1937). The Finnish philosopher Jaakko Hintikka (b. 1929) pursued Carnap's studies on inductive logic. Hintikka's article "A Two-Dimensional Continuum of Inductive Methods" in Aspects of Inductive Logic, edited by J. Hintikka and P. Suppes, and extended the methods Carnap used in The Continuum of Inductive Methods, 1952. Roughly speaking, Carnap defined a system of inductive logic in which there is a one-to-one correspondence between the function that gives the degree of confirmation of a statement and the function that gives the estimated relative frequency. The exact relationship between these two functions depends on only one parameter Carnap called Lambda; it can assume all real values between 0 and infinity (thus the system is a continuum of inductive methods). Every value of Lambda defines a different method for evaluating the degree of confirmation. However, the probability of a universal law is always 0. Hintikka added a second parameter he called Alfa so that the system became a two-dimensional continuum. When Alfa = infinity, Hintikka's system is identical with Carnap's one-dimensional system. Otherwise the two-dimensional system gives a reasonable degree of probability to universal laws even in an infinite universe.

The Danish philosopher Joergen Joergensen (1894-1969) actively collaborated with logical positivists. After Hanh's death (1934) he became an editor of the Vienna Circle's series Einheitswissenchaft, and later he collaborated on the International Encyclopedia to which he contributed the essay The Development of Logical Empiricism, 1951.

Finally, it must be noted that logical positivism played a very important role in the development of contemporary philosophy, not only for its philosophical principles, but also for its editorial and organizational activities. Popper and Kuhn published their most known and seminal works in the logical positivist series. This fact, however, does not prove that Popper and Kuhn were logical positivists, but it does show the movement's broad-mindedness, its kindly disposition, and its influence.

 The American Period Michael Friedman’s Analysis of Logical Positivism