Earley Sr, Joseph E.  "Towards a Reapprehension of Causal Efficacy."  Process Studies 24 (1995): 34-8.

Abstract

Whitehead held that actual entities (occasions) are based on feelings (prehensions) of the antecedent world.  He considered both "simple" and "transmuted" (combined) feelings.  The notion that some interactions are "simple" was consistent with the dominant thrust of the science of the first third of this century, marked by triumphs of analysis such as identification of neutrons and protons as component of atomic nuclei.  The science of the last third of the century is rather different with greater emphasis on synthesis and on complexity.  It now seems clear that "simple" feelings are abstractions.  All concrete interactions are composite ("transmuted").  [Abstract from The Philosopher's Index]