In the fifth sentence of the fourth paragraph ("And in certain... true"), the author italicizes the verb "is" primarily to emphasize

-an area of agreement between himself and another author whose views he has challenged
-an area of disagreement between himself and another author whose views he generally agrees
with
-the equivalence he sees between two seemingly different claims
-the equivalence he sees between two seemingly different terms
-the equivalence he sees between two seemingly different processes