Wassermann, Christoph.  "The Relevance of 'An Introduction to Mathematics' to Whitehead's Philosophy."  Process Studies 17, no.3 (Fall 1988): 181-92.

Abstract

Whitehead's ideas on the nature of mathematics appearing in his first nontechnical mathematical publication IM can be seen as mathematical roots for the development of his later philosophy.  It is argued that his insight into the abstract nature of mathematics led him to develop the concept of an "eternal object," with the applicability of abstract mathematics to the experience of nature issuing in the concept of the "ingression" of eternal objects in actual events.  [Abstract from The Philosopher's Index]