Former Justice Stevens Speaks

The Atlantic has a short interview with former Supreme Court Justice John Paul Stevens available on its web site.  I don't know if he is stating the obvious with this one question and answer:

You say that justices are "playing the role of advocate [during oral argument] more than they should." Advocates for what?

 Often you go into an oral argument and you've made up your mind on a case and you want to convince your colleagues.

Was this covered in Stern and Gressman? Justice Stevens answers the very next question by stating some of the advocacy could be ideological.  Have any particular colleague(s) in mind?  The complete interview is here.  [MG]