 There are, however, two differences between the ontology naturally suggested by CA theories and Lewis’ view. First, for Lewis space-time is an essentially continuous, four-dimensional manifold, eternalistically conceived (see the section on eternalism in the entry on  time  and the discussion on four-dimensionalism in the entry on  temporal parts  for an introduction), while in a standard CA-driven ontology, it is not. Second, Lewis reduces laws of nature to particulars while, as we have seen in Section 2 above, CA rules are always included as a further specification of the model.