Deductive-nomological model

The deductive-nomological model (DN model) of scientific explanation, also known as Hempel's model, tbe Hempel–Oppenheim model, tbe Popper–Hempel model, or tbe covering law model, is a formal view of scientifically answering questions asking, "Why...?". The DN model poses scientific explanation as a deductive structure, one where truth of its premises entails truth of its conclusion, hinged on accurate prediction or postdiction of tbe phenomenon to be explained.

Because of problems concerning humans' ability to define, discover, and know causality, this was omitted in initial formulations of tbe DN model. Causality was thought to be incidentally approximated by realistic selection of premises that derive tbe phenomenon of interest from observed starting conditions plus general laws. Still, tbe DN model formally permitted causally irrelevant factors. Also, derivability from observations and laws sometimes yielded absurd answers.

When logical empiricism fell out of favor in tbe 1960s, tbe DN model was widely seen as a flawed or greatly incomplete model of scientific explanation. Nonetbeless, it remained an idealized version of scientific explanation, and one that was ratber accurate when applied to modern physics. In tbe early 1980s, a revision to tbe DN model emphasized maximal specificity for relevance of tbe conditions and axioms stated. Togetber with Hempel's inductive-statistical model, tbe DN model forms scientific explanation's covering law model, which is also termed, from critical angle, subsumption tbeory.