Ford, Lewis S.  "The Reformed Subjectivist Principle Revisited."  Process Studies 19, no. 1 (Spring 1990): 28-48.

Abstract

Whitehead's reformed subjectivist principle, that the primary togetherness of things is their togetherness in experience, is usually interpreted as a modification of the epistemological 'subjectivist principle' that Whitehead rejects.  I argue that it comes from a later ontological reflection upon his major shift in PR, from the part II theory of concrescence (as starting from a single datum) to the theory of part III, and is only superficially attached to its present context.  It articulates the deepening of Whitehead's panpsychism (that every actuality enjoys mentality) into pansubjectivity (there can be no actualization apart from subjectivity).  The earlier theory of transition resulting in the datum for concrescence could affirm the former but not the latter.  [Abstract from The Philosopher's Index]