  Ayer also repudiated causal necessity. Following Hume, he thought causation could be reduced to regularity: “c causes e” is equivalent to “whenever c then e”. This latter proposition is then a law of nature, which is just a generalization to which we have a certain attitude. So contingent generalizations and laws of nature are much the same; they differ only in that we rely on the latter more than the former, and are prepared to treat the law as though it possessed some stronger modality, though in fact it does not.