Thanks for your wonderfully sophisticated, thorough response. I would love clarification on a few points.
First of all, when should I administer the DES? As a matter of protocol, with every client in the first or second session? Or only with clients whom I get the feeling may have dissociative tendencies?
Secondly, the approach I am referring to is intended to be derived from (perhaps imperfectly) Roy Kiessling's chapter in EMDR Solutions. I believe he talks about accessing "the basketball player"(a relatively imperturbable high school self) for a client who wants to be unruffled by antagonists in board meetings. Does that ring a bell? And how does my description differ from Kiessling's recommendations?
And finally, I would like some clarification about the part "looking through the eyes" of the client. Is it, in nonDID clients, advisable to have the client actually imagine becoming the part(rather than simply being in relationship to the part)? What I understand you to be saying is that as long as there is an observing, intact, adult ego, this experience of becoming another part will only lead to greater maturity and integration. I am not sure, though, if I understood you correctly.
You lost me a little bit with the reference to cathexis. I have no official psychoanalytic training, and have little more than a superficial understanding of that term.