 More than a decade later than the first publication of the DN model, Hempel (1965: 351n) suggested replacing the notion of cause by the notion of antecedent conditions along the lines of the DN model. Moreover, he then distinguishes more carefully between laws of succession and laws of coexistence (1965: 352). Only the former give rise to causal explanations. If a DN explanation is based on laws of coexistence, this explanation does not qualify as causal. A case in point is the law that connects the length of a pendulum with its period: