I have a question about negative thoughts in CBT. Let me give two examples:

Suppose I think about how the school I went to is second-rate, and how this means I will never amount to anything, and thus I get depressed. I could try to refute this thought by telling myself things such as

* Just because the school is second-rate, doesn't mean I am.
* There are many people who graduated from there who went on to be very successful, so it doesn't follow that I won't.
* It's kinda meaningless to rank schools anyway, because so much depends on the student.

and so forth. However, it seems to me that the root of the problem lies not in that thought itself, but in another assumption I hold, which is that "I am a worthless person if I don't have a successful career".

Another example:

Let's say I often engage in mind-reading, where I believe other people are judging me. Every time I have a conversation with someone, I assume that the look on their face means they have a negative view toward me, and this makes me anxious. Again, I could tell myself

* I have no idea what they're really thinking about me.
* They might actually be thinking something positive, and I'm just misreading their face.
* They might have indigestion, and that's why they have that look.

But again, I think the real problem is that I believe "people must not think anything negative about me, or it means I'm a horrible person." I could actually imagine myself being the kind of person who walks around all day imagining everyone is thinking horrible things about him, and yet still never gets anxious because I just don't care what people think!

So, my question is: is it not more important to go after those core beliefs than it is to refute those surface thoughts? Why do so many books that I read on CBT spend time telling you how to refute thinking errors that really don't seem to be what causes the problems in the first place?