Suppose you have a brain that has a tendency to self doubt more than others. How would an agent, after analyzing a claim, coming up with a belief, and then doubting his belief, know if the doubt should be made for genuine reasons (such as a lack of evidence for that belief) or because of his tendency to self doubt?
Allow me to illustrate this with an example. Suppose you come across the scene of a murder. You have all the evidence that indicates John did it. You consult with other detectives who agree. There are fingerprints of John on the deceased’s neck, John had a clear incentive to kill the deceased based on the fact that he was in an abusive relationship with the deceased, etc etc.
Suppose, for some reason though, that you still feel doubt. How can you now know if this doubt is because you truly don’t have enough evidence to state that John murdered her or whether it’s because you just have a tendency to self doubt. Note that since you can technically doubt anything, the tendency, even if it seems to appear genuine, will always have some reason attached to it. It is not as if you just experienced the feeling: you may have some reason that you can imagine the absence of that would remove the doubt. For example, you might think “well what if it’s John’s twin? If I knew for a fact that John did not have a twin, I would not have this doubt.”
So in essence, because this tendency to self doubt may always appear to come for genuine reasons, even when that doubt may not be warranted, how does one know as a matter of fact if his current state of doubt is truly warranted?