As noted in the previous post, one of the most important breakthroughs in writing your dissertation can come from spotting a gap where something has not yet been discussed. Once writing to fill that gap, it may be helpful to ask yourself what other angles there are to the debate. Or think about if the matter went to an official debate or, for law dissertations, to court. Think about creative arguments that an advocate might run and try to develop them yourself. Such development can lead to your getting a first rather than a 2:1.