Hempel’s Theory of Explanation
According to Hempel, an explanation is:
…an argument to the effect that the phenomenon to be explained …was to be expected in virtue of certain explanatory facts. (1965 p. 336)
Hempel claimed that there are two types of explanation, what he called ‘deductive-nomological’ (DN) and ‘inductive-statistical’ (IS) respectively.” Both IS and DN arguments have the same structure. Their premises each contain statements of two types: (1) initial conditions C, and (2) law-like generalizations L. In each, the conclusion is the event E to be explained:
C1, C2, C3,…Cn
L1, L2, L3,…Ln
The only difference between the two is that the laws in a DN explanation are universal generalizations, whereas the laws in IS explanations have the form of statistical generalizations. An example of a DN explanation containing one initial condition and one law-like generalization is:
C. The infant’s cells have three copies of chromosome 21.