Deductive-nomological model
Formal model posing scientific explanation as deductive structure.
The deductive-nomological model (DN model) is a formal view of scientific explanation that poses explanation as a deductive structure where the truth of premises entails the truth of the conclusion. Also known as Hempel's model, the Hempel–Oppenheim model, the Popper–Hempel model, or the covering law model, it was a central concept in logical empiricism and remains an idealized version of scientific explanation, particularly accurate when applied to modern physics.
- field
- Philosophy of science
- known_for
- Formal model of scientific explanation as deductive structure hinged on prediction or postdiction
- also_known_as
- Hempel's model, Hempel–Oppenheim model, Popper–Hempel model, covering law model
Lore & Background
The DN model received its most detailed, influential statement by Carl G. The model holds to a view of scientific explanation whose conditions of adequacy are derivability, lawlikeness, empirical content, and truth. A law in the DN model axiomatizes an unrestricted generalization from antecedent to consequent by conditional proposition and has empirical content testable, differing from mere true regularity by supporting counterfactual claims. The phenomenon to be explained is the explanandum, while the premises to explain it are the explanans, containing at least one universal law and entailing the explanandum. Because of problems concerning humans' ability to define, discover, and know causality, causality was omitted in initial formulations of the DN model. The model formally permitted causally irrelevant factors, and derivability from observations and laws sometimes yielded absurd answers. When logical empiricism fell out of favor in the 1960s, the DN model was widely seen as a flawed or greatly incomplete model of scientific explanation. Nonetheless, it remained an idealized version, and in the early 1980s a revision emphasized maximal specificity for relevance of conditions and axioms. Together with Hempel's inductive-statistical model, the DN model forms scientific explanation's covering law model, also termed subsumption theory.
Reader's Guide
The DN model was a cornerstone of logical empiricist philosophy of science, representing an attempt to formalize scientific explanation as a deductive argument from universal laws and initial conditions. Its significance lies in its rigorous articulation of the covering law conception, which dominated philosophy of science for decades while physics remained the model science. However, the model's decline paralleled the fall of neopositivism in the 1960s, as critics pointed to its allowance of causally irrelevant factors and its inability to account for explanations in biology and other special sciences that rely on causal mechanisms rather than universal laws. The rise of molecular biology, with its focus on causal mechanisms, further challenged the DN model's adequacy. Despite its flaws, the DN model remains an influential idealized standard and a key reference point in debates about the nature of scientific explanation.
Did You Know?
- The term 'nomological' is derived from the Greek word νόμος or nomos, meaning 'law'.
- The DN model formally permitted causally irrelevant factors in explanations.
- The DN model and Hempel's inductive-statistical model together form the covering law model, also termed subsumption theory.
- In the early 1980s, a revision to the DN model emphasized maximal specificity for relevance of conditions and axioms.
Frequently Asked Questions
Who is behind the Deductive-nomological model?
The DN model is most closely associated with Carl Hempel and Paul Oppenheim, who formalized it as a framework for understanding how scientific explanations work. It also carries Karl Popper's name in some references, reflecting the broader logical empiricist tradition it emerged from.
What exactly does the Deductive-nomological model do?
It treats scientific explanation as a deductive structure in which the truth of the premises logically guarantees the truth of the conclusion. In practice, a phenomenon counts as explained when it can be derived from general laws plus specific initial conditions.
What other names is the Deductive-nomological model known by?
Fans and scholars also call it Hempel's model, the Hempel–Oppenheim model, the Popper–Hempel model, or the covering law model. All of these labels point to the same formal account of explanation in the philosophy of science.
Why is the Deductive-nomological model considered important in philosophy of science?
It served as a central pillar of the logical empiricist movement and gave philosophers a precise, formal criterion for what counts as a genuine scientific explanation. Even today it functions as an idealized benchmark, especially when applied to the clean mathematical structures of modern physics.
Where does the Deductive-nomological model work best?
The model is particularly well-suited to modern physics, where explanations often take the form of deriving specific outcomes from fundamental laws and boundary conditions. It is less naturally applicable to the probabilistic or narrative-driven explanations common in the biological and social sciences.
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