Werth, Lee F.  "The Untenability of Whitehead's Theory of Extensive Connection."  Process Studies 8, no. 1 (Spring 1978): 37-44.

Abstract

Whitehead's account of the perceptive mode of presentational immediacy, as he explicitly states, is dependent upon a definition of straight lines in terms which make no appeal to measurement (unlike the definition, 'the shortest distance between two points'): "it is to be noted that this doctrine of presentational immediacy and of the strain-locus entirely depends upon a definition of straight lines in terms of mere extensiveness" (PR 493; cf also 495-496).  The definition of a straight line requires that some geometrical elements be "incident" in another geometrical element.  But this definition contradicts a derivable theorem that "no" geometrical element "a" is ever incident in a geometrical element "b".  It follows that Whitehead's geometrical account is untenable.  [Abstract from The Philosopher's Index]