I actually prefer ambiguity in many situations, though I guess I haven't thought much about how that plays out in therapy. I think I prefer ambiguity because I had a very physically sick person in my family when I was growing up, and for me the only bit of hope came from ambiguity inherent in the situation. (If one were seeking certainty, it would be obvious that this person was going to die.) So I tend to think of ambiguity as where the hope lies, and I tend to think of craving for certainty as the urge to hurtle knowingly toward one's doom.