I particularly like his third point:
I often write about having a sense of purpose. This sense that the work is important is the same thing, I think. And I like the point that we can feel that something is important without necessarily being able to explicate the importance or eloquently put all our ideas into words.
First of all, a dissertation topic must be important to you. If it is not important to you, then discard it and move on to another topic. If it does not seem important to anyone else yet, then do not worry quite yet. Sometimes, it takes time to communicate the importance of a dissertation topic to others. Sometimes, it takes time to articulate that importance out loud. As long as it continues to feel important, keep working on it. The clarity of communication will come sooner or later.
There are times when something seems important to you, but when others help you look at it, you can see that it is not as important as you thought it might be. Life is sometimes like this. Move on, but do not move on until you feel in your heart that you were wrong in the first place. It is better to be too bold than to be too timid in this case. All you risk losing is a little bit of extra time.