BA principle: To be effective a business analyst needs a deep domain understanding.
The role of a business analyst is to facilitate change where the change results in an increase of value.
In order to determine if the change will result in an increase in value, a business analyst has to understand the domain. He needs an understanding of the paradigms, ideas, vision, frameworks, language, that makes up the domain. Once these high-level ideas are understood, they can be related to other domains. If the ideas are similar, the effect of changing the ideas should be similar.
The domain needs to be understood at the level where the change makes sense. Often this is at a higher level than the project or engagement. At the project level, there may be value created, but when looking at the organization level there may not be value created.
This is what makes business analysis enjoyable, it is looking at a problem from many different perspectives and viewpoints, where those perspectives and viewpoints are at many different levels. It is a puzzle where the solving of the puzzle makes the whole better.