ABSTRACT
This chapter shows that a scientific explanation of nature requires the notion of causal power, and suggests some elements for the analysis of the notion. It distinguishes that scientific activity is focused on the finding not so much of laws than of entities and powers, observed regularities and law-like statements are often indicators of such entities and powers. The chapter discusses prediction and explanation: Kepler's laws describe the motions of the planets, which are in turn explained by the theory of gravitation. To ascribe a vis dormitiva to opium, a causal power to an individual or to a kind, is not to explain an observed change, but it is to indicate that the change is due to such and such an agent, of such and such a kind, with such and such property, and that the explanation is to be found in the nature of the kind or of the property.
