Are there any 'blank slate' therapists left? Even Freud wasn't a blank slate. Didn't he have dinner with some of his patients? And of course, one was his own daughter!

I think we do know our therapists, even if we know very few facts about them.

The reason for them actually being there, is because they do have their own personalities which challenge our fantasies and projections. It wouldn't be very therapeutic if we were simply conversing with a fantasy therapist, most of us do that in between sessions anyway!

They aren't interchangeable because one size does not fit all. It's all about the client/t fit.