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The deductive-nomological model (DN model), also known as Hempel's model or Hempel–Oppenheim model or Popper–Hempel model or Covering Law Model, is a formal view of scientifically answering questions asking, "Why...?". DN model poses scientific explanation as a deductive structure—that is, one where truth of its premises entails truth of its conclusion—hinged on accurate prediction or postdiction of the phenomenon to be explained. Through problems concerning humans' ability to define, discover, and know causality, DN model's initial formulation omitted it, thought to be incidentally approximated by realistic selection of premises that ''derive'' the phenomenon of interest from observed, starting conditions plus general laws. Still, DN model formally permitted causally irrelevant factors. Also, derivability from observations and laws sometimes yielded absurd answers. Upon logical empiricism's 1960s fall, DN model was concluded a flawed or greatly incomplete model of scientific explanation, but remained an idealized version, and rather accurate for modern physics. In the early 1980s, revision to DN model emphasized ''maximal specificity'' for relevance of the conditions and axioms stated. Together with Hempel's inductive-statistical model, DN model forms scientific explanation's covering law model, as also termed, from critical angle, ''subsumption theory''. == Form == The term ''deductive'' distinguishes DN model's intended determinism from the probabilism of inductive inferences.〔 The term ''nomological'' follows the Greek word ''νόμος'' or ''nomos'', meaning "law".〔Woodward, ("Scientific explanation" ), §2 "The DN model", in ''SEP'', 2011.〕 DN model holds to a view of scientific explanation whose ''conditions of adequacy'' (CA), semiformal but stated classically, are ''derivability'' (CA1), ''lawlikeness'' (CA2), ''empirical content'' (CA3), and ''truth'' (CA4).〔James Fetzer, ch 3 "The paradoxes of Hempelian explanation", in Fetzer, ed, ''Science, Explanation, and Rationality'' (Oxford U P, 2000), (p 113 ).〕 In DN model, a law axiomatizes an unrestricted generalization from antecedent ''A'' to consequent ''B'' by conditional proposition—''If A, then B''—and has empirical content testable.〔Montuschi, ''Objects in Social Science'' (Continuum, 2003), (pp 61–62 ).〕 A law differs from mere true regularity—for instance, ''George always carries only $1 bills in his wallet''—by supporting counterfactual claims and thus suggesting what ''must'' be true,〔Bechtel, ''Philosophy of Science'' (Lawrence Erlbaum, 1988), (ch 2 ), subch "DN model of explanation and HD model of theory development", pp 25–26.〕 while following from a scientific theory's axiomatic structure.〔Bechtel, ''Philosophy of Science'' (Lawrence Erlbaum, 1988), (ch 2 ), subch "Axiomatic account of theories", pp 27–29.〕 The phenomenon to be explained is the ''explanandum''—an event, law, or theory—whereas the premises to explain it are ''explanans'', true or highly confirmed, containing at least one universal law, and entailing the explanandum.〔Suppe, "Afterword—1977", "Introduction", §1 "Swan song for positivism", §1A "Explanation and intertheoretical reduction", (pp 619–24 ), in Suppe, ed, (''Structure of Scientific Theories'', 2nd edn ) (U Illinois P, 1977).〕〔 Thus, given the explanans as initial, specific conditions ''C1, C2 . . . Cn'' plus general laws ''L1, L2 . . . Ln'', the phenomenon ''E'' as explanandum is a deductive consequence, thereby scientifically explained.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Deductive-nomological model」の詳細全文を読む スポンサード リンク
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