Deductivenomological

Deductive-nomological explanation, sometimes written as deductive-nomological (and occasionally rendered as a single word such as deductivenomological), is a classic model of scientific explanation associated with the philosophy of science. Proposed by Carl Hempel and Paul Oppenheim in the 1940s, it characterizes explanation as a deductive derivation of a phenomenon from general laws and preceding conditions.

In this framework, an explanation consists of an explanandum (the statement of the phenomenon to be explained) and an explanans (the set of statements that account for it). The explanans typically includes one or more general laws or law-like generalizations (nomological statements) together with premises about specific initial conditions or events (the particular facts). If the explanans logically entails the explanandum, the explanation is considered adequate.

The standard form involves two parts: a major premise (a law or law-like generalization) and a minor premise (specific conditions). From these, a deductive inference yields the explanandum. In practice, DN explanations are often used to show how a particular event fits within a broader lawful framework, such as deriving a specific astronomical alignment from gravitational laws.

Critiques of the model focus on its applicability to probabilistic explanations, causal content, and cases where genuine laws are absent or underdetermined. Alternatives and refinements include deductive-statistical explanations, covering-law variants, and mechanistic or causal accounts that emphasize explanatory relevance beyond purely deductive derivation.

Today, DN explanations remain a foundational reference in the philosophy of science, illustrating a formal aim of explanation: to show that phenomena occur as expected given known laws and initial conditions.