I think B is a valid reason, and possibly the true one. C may be true, but I think the belief "I'm inadequate" could lead to anticipating failure at some task or goal, and the belief "I'm adequate" could lead to anticipating success. Also, since the patient already believes e is inadequate, the motivated skepticism is in the opposite direction from es current belief--essentially compensating for an existing bias. Playing biases off each other isn't the best way to get the truth, but it is sometimes the best way available.
Oh, btw, the formatting on the links didn't work quite right.
Summary: Cognitive therapy may encourage [motivated cognition](http://lesswrong.com/lw/km/motivated_stopping_and_motivated_continuation/). My main source for this post is Judith Beck's [Cognitive Therapy: Basics and Beyond](http://www.amazon.com/Cognitive-Therapy-Judith-Beck-Phd/dp/0898628474/ref=sr_1_1?s=books&ie=UTF8&qid=1290418167&sr=1-1)
"[Cognitive behavioral therapy](http://en.wikipedia.org/wiki/Cognitive_behavioral_therapy)" (CBT) is a catch-all term for a variety of therapeutic practices and theories. Among other things, it aims to teach patients to modify their own beliefs. The rationale seems to be this:
(1) Affect, behavior, and cognition are interrelated such that changes in one of the three will lead to changes in the other two.
(2) Affective problems, such as depression, can thus be addressed in a roundabout fashion: modifying the beliefs from which the undesired feelings stem.
So far, so good. And how does one modify destructive beliefs? CBT offers many techniques.
Alas, included among them seems to be motivated skepticism. For example, consider a depressed college student. She and her therapist decide that one of her bad beliefs is "I'm inadequate." They want to replace that bad one with a more positive one, namely, "I'm adequate in most ways (but I'm only human, too)." Their method is to do a worksheet comparing evidence for and against the old, negative belief. Listen to their dialog:
[Therapist]: What evidence do you have that you're inadequate?
[Patient]: Well, I didn't understand a concept my economics professor presented in class today.
T: Okay, write that down on the right side, then put a big "BUT" next to it...Now, let's see if there could be another explanation for why you might not have understood the concept other than that you're inadequate.
P: Well, it was the first time she talked about it. And it wasn't in the readings.
Thus the bad belief is treated with suspicion. What's wrong with that? Well, see what they do about evidence against her inadequacy:
T: Okay, let's try the left side now. What evidence do you have from today that you are adequate at many things? I'll warn you, this can be hard if your screen is operating.
P: Well, I worked on my literature paper.
T: Good. Write that down. What else?
(pp. 179-180; ellipsis and emphasis both in the original)
When they encounter evidence for the patient's bad belief, they investigate further, looking for ways to avoid inferring that she is inadequate. However, when they find evidence against the bad belief, they just chalk it up.
This is not how one should approach evidence...assuming one wants correct beliefs.
So why does Beck advocate this approach? Here are some possible reasons.
A. If beliefs are keeping you depressed, maybe you should fight them even at the cost of a little correctness (and of the increased habituation to motivated cognition).
B. Depressed patients are already predisposed to find the downside of any given event. They don't need help doubting themselves. Therefore, therapists' encouraging them to seek alternative explanations for negative events doesn't skew their beliefs. On the contrary, it helps to bring the depressed patients' beliefs back into correspondence with reality.
C. Strictly speaking, this motivated cognition does not lead to false beliefs because beliefs of the form "I'm inadequate," along with its more helpful replacement, are not truth-apt. They can't be true or false. After all, what experiences do they induce believers to [anticipate] (http://lesswrong.com/lw/i3/making_beliefs_pay_rent_in_anticipated_experiences/)? (If this were the rationale, then what would the sense of the term "evidence" be in this context?)
What do you guys think? Is this common to other CBT authors as well? I've only read two other books in this vein (Albert Ellis and Robert A. Harper's [A Guide to Rational Living](http://www.amazon.com/Guide-Rational-Living-Albert-Ellis/dp/0879800429/ref=sr_1_1?s=books&ie=UTF8&qid=1290418180&sr=1-1) and Jacqueline Persons' [Cognitive Therapy in Practice: A Case Formulation Approach](http://www.amazon.com/Cognitive-Therapy-Practice-Formulation-Approach/dp/0393700771/ref=sr_1_2?s=books&ie=UTF8&qid=1290420954&sr=1-2)) and I can't recall either one explicitly doing this, but I may have missed it. I do remember that Ellis and Harper seemed to conflate instrumental and epistemic rationality.