Synthese (1999), 1-18
I examine two aspects of Hempel's covering-law models of explanation. These are (i) nomic subsumption and (ii) explication of the concept of law by models. In the light of counterexamples some theorists of explanation have abandoned nomic subsumption. Here I examine the prospects for retaining nomic subsumption by rejecting (ii). It is a mistake to imagine that a limited quantity of information about laws and antecedent conditions will be able to provide an actual explanation - other information, about explanations, may be relevant. Instead we may consider two 'structural' approaches. One is holistic - explanation in considered in connection with the systematic conception of laws of nature. The second, supervenience, view concentrates on the 'vertical' structure of explanations, whereby the existence of a nomic explanation at one level reflects explanations on lower levels on which it supervenes.