Emmet, Dorothy.  "How Near Can a Cause Get to Its Effect."  The Philosophical Quarterly 38 (Oct. 1988): 455-70.

Abstract

If a cause is an immediate antecedent of its effect in a time series, whose continuity is dense, there will be infinite intermediaries.  If cause and effect coincide at a point, this also presents problems.  So causation is said to occur as a transaction in overlapping processes, where an overlap can be diminished as by Whitehead's method of extensive abstraction, amended by Russell's notion of compresence to bring in a time dimension.  A cause is selected from the previous history in one of the processes and the effect from the subsequent history of the other, there being a pragmatic element in the selection.  However, there must have been an actual overlap to allow a causal episode.  [Abstract from The Philosopher's Index]