Carl Gustav Hempel

Carl Gustav Hempel (born January 8, 1905, in Oranienburg, Germany; died November 9, 1997, in Princeton, New Jersey) was a philosopher of science and a major figure in 20th-century logical positivism. He is especially well-known for his defense of the Deductive-nomological model of scientific explanation and for his work on the Raven paradox.

Biography

Hempel — known as "Peter" since his school days — studied first at the Realgymnasium in Berlin. In 1923 he was admitted to the University of Göttingen, where he studied mathematics with David Hilbert and symbolic logic with Henirich Behmann. He was especially impressed with Hilbert's effort to base mathematics on a solid logical foundation by deriving it from a limited number of axioms; this attempt is known as(Hilbert's Program).

Also in 1923 Hempel moved to the University of Heidelberg, where he studied mathematics, physics, and philosophy. From 1924 he studied at the University of Berlin where he met Hans Reichenbach, who introduced him to the Berlin Circle of philosophers. Hempel attended Reichenbach's courses. He also studied physics with Max Planck and logic with John von Neumann. In 1929 Hempel participated in the first conference on scientific philosophy organized by the logical positivists. He met Rudolf Carnap there and became enthusiastic about Carnap's work; Hempel therefore moved to Vienna and became part of the Vienna Circle, attending courses with Carnap, Schlick, and Waismann. In 1934 he received his doctoral degree from the University of Berlin with a dissertation on probability theory.

The same year he fled the increasingly repressive Germany and emigrated to Belgium with the help of a friend of Reichenbach, Paul Oppenheim. With Oppenheim, Hempel co-authored the book "Der Typusbegriff im Lichte der neuen Logik" on typology and logics in 1936.

In 1937 Hempel emigrated to the US where he accepted a position as Carnap's assistant at the University of Chicago. Subsequently he held positions at New York's City College (1939-1940), Queens College of New York (1940-48), Yale University (1948-1955), and Princeton University (1955-64) where he was Stuart Professor of Philosophy and where taught alongside Thomas Kuhn, and stayed until he was given emeritus status in 1964. As an emeritus he spent the years from 1964-1966 at the Hebrew University in Jerusalem and also taught at Berkeley and The University of California at Irvine. He joined the faculty of the University of Pittsburgh in 1976, where he was University Professor of Philosophy until 1985. He was the last surviving member of the Vienna Circle.

He never embraced the term "logical positivism" as an accurate description of the Vienna Circle and Berlin Group in which he had participated during the years between the World Wars, preferring to describe those philosophers, and himself, as "logical empiricists."

Hempel's first wife, Eva Ahrends Hempel, died in 1944. His second wife, Diane Perlow Hempel, survived him. He had two children, a son Peter Andrew Hempel, and a daughter Toby Anne Hempel. Adolf Grünbaum said of Hempel, "He was at once one of the great philosophers of science of the 20th century and also one of the most wonderful human beings that one could encounter anywhere." Grünbaum also called Hempel's work on the theory of scientific explanation the point of departure for all other theories of scientific explanation in the 20th century.

In 2005 the City of Oranienburg renamed a street to "Carl-Gustav-Hempel-Straße".

Scientific Explanation

Until later in his life, Hempel was best known for producing in 1948, with Oppenheim, what is known as the Deductive-Nomological (or Covering-Law) Model of science, an account that made scientific explanation and prediction equivalent. According to this view, a scientific explanation of a fact is a deduction of a statement (called the explanandum) of the fact we wish to explain; the premises of the deduction (the explanans) are scientific laws (whence the term "nomological") plus initial conditions. The explanans must be true for the explanation to be acceptable.

This view — a typical and central view of logical positivism, or logical empiricism as Hempel preferred to call it — reduces a scientific explanation to a logical relationship between statements. The explanandum is a logical consequence of the explanans. The view requires scientific laws, and facts are explained when they are subsumed under laws. This led to questions about the nature and status of scientific laws.

Hempel and Oppenheim held that a fundamental theory is a true statement with quantifiers ("all," "some," "none") and without individual constants ("John," "that bird that has the cut on its beak"). A derived theory is a generalized statement that is a consequence of a fundamental theory. Hempel, and the logical positivists as a group, held the view that a scientific theory deals with general properties, and these properties are expressed by universal statements (e.g., the example that was often used was "All ravens are black"). Statements referring to specific space-time regions or individual entities were not allowed. The example often given was Newton's laws: They were supposed to be true for all bodies in any space at any time.

There are, however, scientific laws that are true under limited conditions and that refer to specific entities, such as the Sun or one of its planets. To deal with this, Hempel and Oppenheim distinguished between a fundamental theory, which is universal and has no temporal or other restrictions, and a derived theory that can make reference to individual things with their individual characteristics.

The Hempel-Oppenheim model required that scientific theories be true and not just tools for making predictions. This means that their theory assumed or entailed scientific realism. [For more on this, see the article "Carl Gustav hempel (1905 - 1997") in the Internet Encyclopedia of Philosophy: http://www.iep.utm.edu/h/hempel.htm ]

The Raven Paradox

Hempel, and the Logical Positivists in general, thought that scientific generalizations were universal statements (general hypotheses) that were confirmed through observation. A typical example of such a statement would be the hypothesis (1) "All ravens are black." But that statement is logically equivalent to and thus can be reformulated as (2) "All non-black things are non-ravens." But statement or hypothesis 2 can be confirmed by observing non-black non-ravens, e.g. white shoes or red cardinals or every other thing that is not black and not a raven. So in order to confirm the hypothesis that all ravens are black, will it do to find as many examples of green blades of grass as possible? Hardly! [See the article Karl Raimund Popper for further discussion of this problem and for Popper's counterproposal, namely falsification instead of confirmation.] Hempel tried to get around this problem by proposing a quantitative method for determining the degree of confirmation of any hypothesis by particular statements of evidence.

The Inductive-Statistical Model

Bibliography

Main Works:

1936 Über den Gehalt von Wahrscheinlichkeitsaussagen
1936 Der Typusbegriff im Licht der neuen Logik, with Paul Oppenheim
1942 The Function of General Laws in History
1943 Studies in the Logic of Confirmation
1950 "Problems and Changes in the Empiricist Criterion of Meaning," 11 Review International de Philosophy 41, pp. 41 - 63.
1959 The Logic of Functional Analysis
1965 Aspects of Scientific Explanation
1966 Philosophy of Natural Science,
1967 Scientific Explanation
2000 Selected Philosophical Essays
2001 The Philosophy of Carl G. Hempel: Studies in Science, Explanation, and Rationality

External links

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