= Solution
The <covering-law model> explains a phenomenon by subsuming it under <scientific laws> and specified circumstances. Its <deductive-nomological model> requires the event to follow by valid <deduction>, with a law used essentially, empirical content and true premises. For example, a dynamical law and appropriate initial conditions can explain a body's later trajectory.<Studies in the Logic of Explanation by Carl Hempel and Paul Oppenheim>[section 3: logical and empirical adequacy conditions]{ref}
This captures an important feature of many physical explanations: the event is shown to fit a wider, independently supported pattern. It makes assumptions explicit and connects explanation with prediction. However, derivability alone does not ensure the right explanatory direction. With a pole, a known solar elevation and a measured shadow, geometry lets us calculate either height from shadow or shadow from height. The <explanatory asymmetry> remains: under the ordinary causal setup, the pole and illumination explain the shadow, rather than its measured length causing the pole's height.
Irrelevant information also exposes a weakness. From a general law plus an unnecessary fact one may still derive the result; logical validity does not show that the added fact helps explain it. Conversely, many accepted explanations are statistical or mechanistic rather than deductions from exceptionless universal laws. Extending the account to the <inductive-statistical model> helps, but a high <conditional probability> does not by itself establish <causal relevance>.
The <covering-law model> is thus a useful account of one important explanatory structure, not a complete criterion of <scientific explanation>. A stronger account must consider which assumptions make a difference, what mechanism operates and why the explanatory direction is appropriate. The model's virtues survive when it is treated as a component of explanation rather than an exhaustive definition.
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