 In Bell (1976) and (1990), Bell derives the factorizability condition from a condition he calls the Principle of Local Causality (see Norsen 2011 for discussion). In (1990) he begins his analysis with a rehearsal of the reason that relativity should be taken to prohibit superluminal causation. On the usual notion of causation, the cause-effect relation is taken to be temporally asymmetric, with causes temporally preceding their effects. In a relativistic spacetime, events at spacelike separation are taken to have no temporal order. Any system of coordinates will assign time coordinates to each of any pair of events, but, if the events are spacelike separated, the time coordinates assigned to a pair of events at spacelike separation will differ in their ordering, depending on which reference frame is being employed. If we take all of these reference frames to be physically on a par, it must be concluded that there is no temporal order between the events, as relations that are not relativistically invariant have no physical significance.