Born in Oranienburg, Germany, Hempel studied mathematics and physics as well as philosophy, at the universities of Göttingen, Heidelberg and Berlin. After a brief period of research in Europe, Hempel migrated to the United States in 1937 and taught at Yale, Princeton and Pittsburgh.
Hempel was strongly influenced by the positivist philosophers of the early twentieth century, notably Reichenbach, Schlick and Carnap, and became a prominent representative of the logical positivist (see LOGICAL POSITIVISM) perspective on knowledge, language and science. Although he stayed largely within the empiricist and scientific framework of positivism, he was also a highly effective internal critic of the positivist excesses, and his many writings, well known for their lucidity and judicious argumentation, contributed greatly to the process of transforming the positivist movement and integrating it with the mainstream philosophy of the English-speaking world.
Hempel’s early critical work on the positivist criterion of meaning (see VERIFICATIONISM) helped to liberalize the restrictive positivist doctrine on what is “cognitively significant” and what is “cognitively meaningless”. His mature views on meaning came to incorporate an important holistic element: whole scientific theories must be taken as the ultimate units of cognitive significance, and it is only when a theory is taken together with its “interpretative system” (i.e. a set of statements in which both “theoretical” and “observational” terms occur) that one can meaningfully speak of its empirical content.
Hempel was among the first to develop precise definitions of “evidence e confirms hypothesis h” and related concepts. His approach was largely formal and syntactical. His celebrated “Raven Paradox” concerning confirmation of generalizations by “positive instances” inspired an active debate in confirmation theory for a number of years (see HEMPEL’S PARADOX OF THE RAVENS).
Hempel’s most influential work by far was on the nature of scientific explanation. According to his “covering-law” conception of explanation, the occurrence of an event is explained by subsuming, or “covering,” that event under a general law. When the covering-laws are deterministic, the explanation takes the form of a deductive argument with laws and statements of antecedent conditions as premises and an appropriate statement describing the event to be explained as its conclusion. Explanations conforming to this deductive model are called “deductive-nomological explanations”. Hempel applied the model to explanations in history, explanations of human actions and functional explanations in biology and the social sciences.
Hempel’s covering-law approach also allowed “statistical explanations,” explanations in which statistical or probabilistic laws are used to show that the event to be explained is made highly probable, rather than deductively necessitated, by the explanatory premisses. The nature of the precise constraints to be placed on this “statistical model” has become a topic of much productive discussion in philosophy of science during the last three decades, spawning numerous alternative models.
Underlying Hempel’s work on explanation are the following two central ideas: first, explanation, or scientific understanding, is not merely a matter of “intellectual satisfaction” but must have an objective, testable basis; second, this testability condition is to be implemented by the requirement that an acceptable explanation must show that the occurrence of the phenomenon to be explained can be rationally expected on the basis of the information contained in the explanatory premisses.
See also BAYESIAN EPISTEMOLOGY in Part I; EXPLANATION.
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Introduction Carl Gustav Hempel was one of a group of philosophers from Central Europe who emigrated to the United States in the 1930s and who profou