Second guessing creative briefs

I read an article from a marketing person recently. They are involved in the creative industry and the article was about briefing a creative.
The take-out from the article was important from both the client and the creative expert perspective. It was that the client needs to be specific about what they want.
After reading that article I could not help but to test that theory. After some further consideration I have found that the statement, 'be specific' is not specific enough.

What if a client doesn't actually know what they need? This is likely the case when they approach a professional design studio for assistance in the first place.
Should a new prospect know what they need and exactly the way they want it presented, then they should really go to a finished artist or desktop publisher to obtain the communication item.
In theory, if we went with the original sentiment about the client being specific, then the designer wouldn't be the best person for the job. This idea has cycled about my little mind for some time and I have some conclusions after further consideration.
The client still needs to be specific - but they need to be specific about the areas where they are not sure how to proceed as well as where they are sure how they want to proceed.
If the client would like the designer to solve the challenge from A - Z - then they also need to be specific about that request.