I'm not thinking so much of emotions with the external world. I think that is clearly an instinctive belief (as Russel said, that wrong bastard), which I consider intuition.
Where I come from, we call those assumptions without which we don´t get anywhere at all "axioms". They aren´t caused by emotions but by necessity. Questioning axioms and putting them on the same level as practically any other kind of assumptions is intellectually desperate.
But maybe I can word the question a bit clearer for you:
Which emotion would be required for us to let go of the assumption that there is something outside our heads? Or: Which emotion would we have to let go off in order to arrive at the conclusions that there is nothing outside our heads?
But I'm thinking more broadly when I speak of emotions: there's no such thing, maybe in any situation, of "just" having an idea or belief *without* an emotion to package it.
No doubt about this but, you know, without a world outside our heads there wouldn´t even be any situation whatsoever, to begin with.
This might be seen in how you Germans use belief, right? From "lief", meaning "wish" (or something)?
The German word "Glaube" covers part of the English words "belief" and "faith", if that´s what you mean.
Ok, now that I have grabbed for my Etymology Duden, I think I found what you are referring for (and which I actually hadn´t known

): "Glaube" has common roots with "lieb" (dear).
Basically for any belief we currently believe, we have at least a slight positive emotional charge which packages the content of this belief.
Would you mind explaining this with two examples, please:
1. I believe that the ebola virus exists. What is the positive emotional charge that packages the content of this belief?
2. What is the emotional charge packaging the belief that there is something outside our heads?
Which explains pretty easily why people aren't changing their ideas every second they find convincing argument to the contrary: they have the intertia of emotion to carry them forward. And definitely explains the people with *very* strong emotional charges for their beliefs and why they get so defensive or clearly upset when their beliefs are questioned.
Yes, that´s certainly true for many beliefs. Then again, I can think of countless beliefs that are either emotionally neutral or downright negatively charged (I´d rather Hitler had not existed, but I believe he did anyway; I like the idea that Shakespeare was the writer of all works published under his name, but I belief that that is not so...).
Enter "cognitive dissonance". Most beliefs charged with negative emotions are held to avoid cognitive dissonance (I hate it that there´s no pot of coffee on, but well, no amount of wishful thinking gets it there, so I am left to believe it isn´t there).
Now, I know what´s coming (changing from a category to the meta-category, pretend that the meta-category includes itself):
Avoiding cognitive dissonance has a positive emotional charge, so avoiding cognitive dissonance is basically the same mechanism as wishful thinking. How did I do?
In any case, that´s where you´d lose me.
Basically anyone interested in rationality as a value also has to have emotional intelligence, insofar as he realizes his emotions getting activated, is able to feel them or access them, and knows how to push through them.
Sure, but that´s not all there is to it. See the coffeepot example. It doesn´t have to do with praise of rationality nor with emotional intelligence - this bloody thing simply isn´t there.
Do you think that if I go deeper into the emotion that makes me believe that the pot isn´t there I might end up believing that the entire world isn´t there? Same mechanism, same emotion - but just lacking the required intensity?
As for the external world, same thing: instinctive belief packaged by an emotion.
Come on, get real:
Which emotion is it that trumps rationality (which, as we all know, dictates that there is no external world) and makes this utterly irrational belief in an external world so irresistably palatable? And more importantly, which emotion would I have to exercise more to reach the state of believing that there is no external world? Must be fun!
Intense skeptics are down with pushing through this emotional tug that goes with this instinctive belief/intuition,
Are these the guys who can´t get out of bed because, well, there is no bed, in the first place?
I mean honestly, Received: When I sit with four person around a table and all of them (despite desiring for a hot coffee) believe that there is no coffee on the table - the reason for this is that they all have a positive emotion towards the absence of coffee? Is that really the most plausible explanation?