Article abstract: Carnap became leader of the logical positivists. They regarded logic, mathematics, and physics as genuine knowledge, but metaphysics and ethics as cognitively meaningless. Carnap’s main strategy was to construct artificial languages in formal symbolism.
Rudolf Carnap was born in northwest Germany to parents who were earnestly religious but tolerant of the beliefs of others. During adolescence, his studies of science led him to drop his religious beliefs in favor of secular humanism. He attended the Universities of Jena and of Freiburg im Breisgau, studying mathematics, physics, and philosophy.
At Jena, between 1910 and 1914, Carnap attended the classes of Gottlob Frege, a philosophical mathematician little known at that time. Frege had anticipated Alfred North Whitehead and Bertrand Russell by originating quantificational symbolism in logic and using it in the attempt to demonstrate rigorously that all mathematics of number is strictly reducible to logic. Under Frege’s influence, Carnap came to distinguish sharply between symbols and what the symbols stand for, thereby avoiding much confusion in the philosophy of mathematics, and also to distinguish sharply between analytic truths (knowable on the basis of principles of pure logic together with explicit definitions) and synthetic truths (knowable only on the basis of some kind of immediate experience). However, Carnap rejected Frege’s metaphysical views about the reality of abstract entities.
Carnap’s studies were interrupted by military service in World War I. On his return, he committed himself to graduate work in philosophy. His doctoral dissertation, published in 1922, dealt with the philosophy of space. It was influenced by the neo-Kantianism he had absorbed from his professors, but it also showed his keen interest in new developments in physics. Soon his philosophical work began to show the influence of Russell, who in 1914 had called for a new breed of thinkers who would resolve philosophical problems by using the techniques of mathematical logic to construct formalized systems.
Carnap’s philosophical career began to blossom in 1925 when he was invited to lecture at the University of Vienna, where Moritz Schlick had assembled a group of philosophers, mathematicians, and scientists actively concerned with the philosophy of science. This group held regular meetings and came to be known as the Vienna Circle. They were impressed by Carnap, and Schlick obtained a teaching position, starting in 1926, in philosophy at Vienna for Carnap. Carnap later looked back on this period as a time of especially fruitful discussion and cooperative research among this lively group of largely like-minded thinkers. Carnap began to play a leading role in the drafting of manifestoes and the editing of publications aimed at spreading the philosophically radical doctrines of this new movement, and his writings soon became more extensive and influential than those of any other member. The movement came to be called logical positivism, though Carnap preferred to call it logical empiricism.
The members of the Vienna Circle had been impressed by Ludwig Wittgenstein’s “Logisch-philosophische Abhandlung” (1921; best known by the bilingual German and English edition title of Tractatus Logico-Philosophicus, 1922, 1961) and drew some of their doctrines from it. However, Wittgenstein did not find Carnap congenial; Carnap’s conception of philosophy could hardly have pleased him. Carnap’s view was that the goal of philosophy should be to work out rational reconstructions of scientific language that needed clarifying. In each case, his strategy was to construct a formalized artificial language containing precisely defined symbols that could serve as improved replacements for the terms occurring in ordinary scientific discourse. For him, these were just technical problems requiring technical solutions. Carnap had no interest in the mystical or in other philosophical perplexities with which Wittgenstein became obsessively concerned.
Carnap’s most important work from his Vienna period was The Logical Structure of the World. In this book, he attempted to sketch a rational reconstruction of all talk about physical objects in the world. He tried to show how, in a formalized language, sentences using physical-object terminology could in principle be completely translated into sentences that merely report immediate sense experience. This was Carnap’s reformulation of the view that earlier philosophers had termed phenomenalism. It became part of the program for what Carnap called the “unity of science,” his goal being a single, logically unified language system in which all science could be expressed.
Russell had already worked on this project, but Carnap’s treatment was fuller. Even Carnap, however, left the project very incomplete, with many logical gaps unbridged. Notably, rather than starting with sentences about small bits of sensory content as Russell had, Carnap, under the influence of Gestalt psychology, began with sentences about momentary total experiences. Also, unlike Russell, Carnap did not think it imperative to treat immediate experience as the starting point. He mentioned that sentences about publicly observable physical objects could also serve as an acceptable starting point. Thus, he showed his cavalier attitude toward the traditional idea that empirical knowledge of objects must be based on private sensory experience. He held that choice of a starting point is merely a matter of convenience.
After five years in Vienna, Carnap moved to the German University of Prague, where he remained through 1935, continuing to maintain contact with his colleagues in Vienna. During his Prague period, he published a very readable short book, Philosophy and Logical Syntax, in which he provides a forceful statement of the overall...
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