Carl Gustav Hempel

Deductive–nomological model

Hempel introduced and defended what is commonly called the deductive–nomological (DN) model of scientific explanation. In this framework an explanation is an argument: a set of premises (the explanans) that, typically by means of one or more general laws, logically entail the event or regularity to be explained (the explanandum). Hempel emphasized conditions such as truth of premises, logical derivability of the explanandum, and the presence of at least one lawlike generalization in the explanans. The DN model unified explanation and prediction under a single logical form, treating both as consequences of law-based reasoning.

Confirmation and the Raven paradox

Hempel also formulated and popularized a puzzle about confirmation now known as the Raven paradox. The paradox arises from two plausible principles: that observational evidence can confirm universal generalizations, and that logically equivalent statements should be equally confirmed by the same evidence. Applying these leads to the counterintuitive consequence that observing a non-black non-raven (for example, a green apple) seems to confirm the claim that all ravens are black. This problem prompted extensive debate and stimulated probabilistic accounts of confirmation and refinements in how scientists and philosophers treat relevance and background knowledge.

Career, writings, and influence

Hempel wrote influential essays and accessible surveys that circulated widely among philosophers and scientists. His clear, formal approach made him a central figure in mid-century discussions of scientific method, and his work remains a standard reference in philosophy of science courses. During his career he taught and lectured internationally, helping transmit logical-empiricist ideas to English-speaking audiences and to subsequent generations of analytic philosophers.

Criticism and legacy

While the DN model clarified many issues, it also faced criticisms: it can misidentify mere subsumption under laws as explanatory in cases that feel uninformative, it struggles with statistical and probabilistic explanations, and it does not by itself capture causal or mechanistic detail that many consider essential. These limits led to alternative models (statistical relevance, causal/mechanistic accounts) that build on, refine, or reject Hempel's strictures. Nevertheless, his formulations set precise problems that advanced the study of explanation, confirmation, and the structure of scientific reasoning.

Key concepts and notable works

• Deductive–nomological (DN) model of explanation
• Explanans and explanandum distinction
• Raven paradox and issues in confirmation theory
• Collected essays and introductory treatments used in philosophy of science