In the story "Everything That Rises Must Converge," why do both Julian and his mother revert to childhood at the end?

One might
understand the words of the mother and son in ironic relation to the title of the story, which
is also the tile of the collection of short stories in which it was published.  Following this
direction of interpretation, the mother rises to childhood innocence as she descends into
death; however, the son, though speaking in the language of a childs love for his mother, does
not rise, but rather remains in a quagmire below his mother, knowing he loved her but will not
be able to demonstrate that to her. One critic puts it this way:  What is left after [the
mothers]...