Nobo, Jorge Luis.  "Transition in Whitehead: A Creative Process Distinct from Concrescence."  International Philosophical Quarterly 19, no. 3 (Sept. 1979): 265-83.

Abstract

Whiteheadians either have construed transition as a mere succession of concrescences and not as a genuine creative process, or have taken transition and concrescence to be one self-same process viewed from two different perspectives.  Against these views, Nobo argues that transition is a creative process begetting a novel but "incomplete" occasion, and that concrescence is the creative process whereby the occasion thus begotten "completes" itself.  Transition, which has the many settled actualities of the universe as its data, at once begets the occasion relative to which that settlement is defined, and also abstractly objectifies that settlement within the occasion.  Concrescence, which has the product of transition as its datum, starts from that datum, reacts to it, and ultimately fuses both the datum and the reactions in the final satisfaction.  [Abstract from The Philosopher's Index]