12.5 Writing a Ph.D. Thesis
The Ph.D. degree is awarded for an original contribution to knowledge. One important function of the Ph.D. thesis is, therefore, to demonstrate that you have made such a contribution. This is where you put the parts of your work together to formulate higher-level conclusions. These are then related to the work of others to define, in a wider sense, how your research has developed the knowledge in your field. A thesis thus contains a more general synthesis than that in a research paper.
As the thesis is the last stop on your journey towards the Ph.D. it is appropriate to briefly discuss its parts here. Though these parts are similar to those of a scientific paper, their functions are different. The following lies close to Phillips and Pugh [3]. Originally, a master's degree was a license to practice, whereas a doctor's degree was a license to teach at university level. To teach with authority, faculty members obviously need to have a deep knowledge of their subject. They need to have a grasp of the current knowledge and be capable of extending it. You demonstrate these abilities through the parts of your thesis.
Just as a scientific paper, a Ph.D. thesis begins with a background. The main purpose, however, is not to prepare the reader for the upcoming analysis. It is to demonstrate that you master the theory in your field to the full professional standard. This is normally accomplished by a literature review of your field but it is not sufficient to just list relevant studies one after the other. To show that you are in command of your subject you must organize the knowledge in a coherent and interesting way. It is important to demonstrate that you understand central theoretical concepts, that you can identify research trends and point to areas of knowledge where there is room for improvement. You should also show that you are able to evaluate the contributions of others and justify your criticism. In addition to this, the background chapter should motivate your own research by spelling out in detail exactly what you are studying and why.
The method chapter of a thesis contains similar information to that in a research paper but its function is mainly to show that you understand and master all the practical aspects of experimentation. For example, in addition to describing which measuring instruments you used, you must devote space to explaining their working principles. Instead of just describing your analysis techniques, you explain the fundamental principles behind them, including a critical discussion of their limitations.
Just as in a paper, results and analysis chapters follow the background and method parts. The extent of these will vary depending on the format of the thesis. If you are writing a monograph, all the data and analyses must be presented in depth within the thesis. In some places, it is more common to write a summary thesis with the published papers as appendices. In such theses the results and analysis chapters are considerably shorter and contain ample references to the papers instead.
The most important part of your thesis is the contribution chapter. This is where you clearly spell out how you have changed the knowledge in your field. In this chapter, you put the conclusions from your work into a wider context. You also describe the limitations of your research, with appropriate suggestions for new work. One might ask why Ph.D. students are expected to evaluate their own work. Isn't this the grading committee's job? Well, the thesis serves to demonstrate that you have become a fully professional researcher with a firm grasp of your field. As a part of this you must show that you are capable of evaluating the impact of research, your own as well as that of others.
The contribution defines the synthesis between the parts of your research and the greater body of knowledge in your field. To put it simply, it explains why and in what way the contents of the background chapter have now changed as a result of your work. From now on, your successors will face a different situation because they have to take account of your research when they plan their own.