Write the abstract

Your abstract will be a small work of art. It will be about 250 words, but will describe your contribution to knowledge in a way that sets it in the context of current work in your academic discipline.
There are major limitations on the style of an abstract. You do not have the luxury of a list of references: the text must be self-contained, and there is obviously little space for any account of your evidence or methods, or for quotations from other work. Even more than the rest of the thesis, the abstract should avoid using the first person, or equivalent phrases like “the author”, since the abstract, like the blurb on the outside of a paperback, is in the style of a review of your work.
The PhD examination is likely to pay particular attention to the wording of the abstract. Everything it promises must be delivered in the thesis in a very obvious way – it is a good idea to ensure that phrases used in the abstract should appear as titles in the table of contents. Thus in miniature it gives an overview of your thesis.
It is a good idea to write a first draft of the abstract quite early on in the research. If you can’t describe your contribution to knowledge in 250 words, you should refine your ideas until you can.
On the other hand, once you have stated your contribution to knowledge in this succinct way, every part of the final thesis will contribute to establishing it. Any material, no matter how clever, that is not directly relevant to this task is likely to be removed from the thesis, either by you or your examiners.