Ignorance is basically the root cause of all negative mind states, whether it is doubt, anger, fear, etc. Ignorance is the root cause, it covers everything including doubt. We can't really say there is a difference between them, one contains the other.
So when we see ignorance, perhaps to identify it in a different way: Let's say you have something like 90 million Germans here and inside the 90 million Germans you have 45 million men, 45 million women, 35 million children, adults etc. So you have these smaller groups inside the big one. Doubt is a specific type of ignorance. So that is basically what we are saying, if you think of any difference, ignorance is just all of the unbeneficial mind states, doubt is a specific one.
Doubt is the one that is the most dangerous compared to virtually all the others. Doubt stops your practice. You have heard me say in the normal 10 day retreat - doubt about the teachers, we start hating the teachers, doubt about the practice, we start hating the practice, doubt about ourselves, we just have self-hatred. So doubt can cripple your whole practice, doubt can stop you, you are finished. You have to try to solve doubt more than any other type of hindrance.
Anger - you know you need to work with it, you basically know what to do, you know you have to do it yourself. Fear the same, whatever, but doubt is more difficult to work on just with yourself. So one of the biggest things for doubt is that you need a good friend.
Doubt is like you are sitting on a fence and you are not sure which side to go. Should you jump down this side, should you jump down the other side, you just don't know. So when you have doubt all you do is to sit on a fence, you don't go anywhere. But we have to make the jump, which way to jump? If you don't know it yourself, you need a good friend. We ask the advice of someone whom we trust, someone whom we respect. And even if they don't give us the exact answer we feel we would like to hear, maybe we should try it anyway, especially when this person has helped us many times before.
That is one thing that many of you all have to face, also. When you come into the interviews with me and Rosemary sometimes we tell you something that is unpleasant, you don't really like that one. But you have come back for more, you know we have given you good advice before, ok, give it a go, try it and see what happens. Because if you just say, "Oh no, I am not going to try that", and then you just go back to sit with your doubt, you still don't go anywhere. Even if you tried something and it doesn't work, then at least you have tried something, and you know, "That one didn't help, it is not ok" and you can switch and go the other way.
So with doubt you have to try to figure out, how to get motivated, how to go somewhere and a good kind friend is the key to it. And if you don't have a good friend available, grab one of your Dhamma books, grab one of your CDs, tapes, listen to them, try to stimulate your mind so that you can perk up that area where the doubt is, so you can find some solutions to it. But don't hold on to doubts for too long. A classic thing that I say every retreat is when you hold on to doubt too long they can turn into aversion. The aversion will cripple you, it will stop your practice, so get to your good friends as quickly as you can.