The PhD thesis guide

This guide was written in the spring and summer 2016. I need to thank my PhD students Grainne Costigan, Paul Dawson, Donna Rodgers-Lee, Laura Rigon, Inna Bozhinova as well as my advisors Jochen Eislöffel and Joerg Isserstedt for implicitly teaching me everything that is in this document.

What is a PhD thesis?

The trivial answer is that a PhD thesis is a book of prose. It is a piece of scholarly writing that qualifies a candidate to obtain a doctoral degree anachronistically called a “Doctor of Philosophy”. This degree then qualifies the successful candidate to pursue a career in academia and to various others endeavours in life.

The real answer is that a PhD thesis is first and foremost a social construct; it evolves through space and through time and even more so through subject matter. And even in a given era and country and subject, the PhD dissertations are allowed to vary significantly in length, style, and substance. Defining a PhD is like holding a piece of soap with wet hands. It keeps slipping away. But that is not a particularly helpful answer if you are sitting in front of an empty document and your scholarship is running out in two months time.

To give a helpful answer, I have to limit myself to my field, astronomy. I do not claim that my criteria for a PhD thesis are shared by all my colleagues and that they will hold in the distant future. I’m simply saying that after writing one PhD dissertation in Germany, supervising five PhD dissertations in Ireland and the UK, examining a few PhD dissertations in the UK, and reading dozens of dissertations from lots of European and American countries I came to the conclusion that there is a useful consensus on what constitutes such a book. It may be ill defined, but it is much better defined than many other text forms, say, an anthem or an essay.

An actual definition

Here comes an actual definition: A PhD thesis has to describe substantial, original, academic research that in principle could be published in a peer-reviewed journal. Let’s take that apart.

First, the thesis has to be substantial enough to qualify as a peer-reviewed publication. Papers in my field are at least a few pages long and are supposed to add something of substance to the subject area. Typical PhD thesis are a few dozen to a few hundred pages long, sometimes excluding lengthy appendices. They are usually longer than just one peer-reviewed publication. A useful guideline is probably to aim for material that could be published (or is in fact published) in three papers.

Second, it has to of an appropriate style to be publishable. Style is a scale-free parameter, it comes into play on all scales, from words to sentences to paragraphs to chapters to the whole thesis. Typos and typesetting issues have to be minimized. Sentences need to be grammatically correct. The sequence of sentences has to create logical arguments. Paragraphs and sections need to follow a coherent structure. The figures and tables need to be clear and fully explained. Basically, it has to be well done. What this means in detail is important to figure out, in cooperation with the supervisor and colleagues.

And third, it has to be contain original research. A PhD thesis is not just a review, although reviewing your field is an essential part of it. A thesis needs to add something that was not there before. This can be observations, data, code, discoveries, ideas, theories, models, facts, connections between facts. A PhD thesis in astronomy has to have something new to say about our understanding of the cosmos. These original thoughts may be wrong, most of them are, but they have to be there. This is the fun part.

These basic criteria for PhD dissertations imply that the PhD is not independently defined. Instead, it is tied to the criteria used in the peer-review process in the scientific literature. Peer-reviewed papers are the gold standard, the only currency that counts. If you publish a few peer-reviewed papers as a PhD student, the dissertation is likely going to be a formality. Vice versa, if you have trouble publishing your work, the PhD process might be a struggle.

This also means that the gatekeepers of the PhD process, the people who determine whether a PhD thesis is a PhD thesis or not, are the peers of the candidate. The supervisor, the examiners, the reviewers, colleagues who have read and commented on the papers. People who have gone through a similar process some time ago. The PhD criteria are not some elusive code that is written down on the walls of a prehistoric cave. They are created and recreated every day, by scholarly communication among peers.

A PhD thesis is not necessarily just a bundle of papers. It can be, if the university allows it. But most universities don’t do that. They want original writing, not just links to papers that are published elsewhere. And there can be important differences between papers and a thesis. A thesis is much more a report of the work that has been done than a presentation of just one specific finding. A lot of research will never get published in a peer-reviewed paper. Research that didn’t go anywhere. Results that were deemed boring or inconclusive. Dark data, grey data, data that lingers in drawers. Unfounded speculations. Figures with uncorrelated datapoints. All this has a place in a thesis.

A PhD dissertation can and should include a much broader introduction than a paper, aimed at a much wider audience. It should be readable by every researcher in the general subject area, in my case astronomy, not just by a handful of experts. Moreso, it should be interesting for a wide audience, not just for a handful of experts. A thesis can be much more personal, in style and content. It can be poetic in places. It can be literary. It can have an actual narrator, in first person singular. But doesn’t have to be. It’s your call. The PhD thesis is a labour of love.

Three years of work, resulting in three peer-reviewed papers, which are then turned into three big thesis chapters, complemented by introduction and conclusions. That could be the formula to aim for. But it very rarely works that way. The first paper might take way too long (it always does), some ideas don’t pan out, other ideas come up, time is lost due to unforeseen circumstances, and so on and so on. This is all completely fine. Your thesis doesn’t have to follow the template.

Plus, there is no template. Every PhD thesis is different. Every PhD candidate is different. And the beauty of the PhD is that there is time to experiment, time to elaborate, time to learn, time to fail. There is a reason why PhD scholarships cover expenses for several years. It’s a long process. And if it doesn’t work out according to the initial plan, that’s perfectly normal. Some crude benchmarks for each year are probably helpful, but it might not work out that way. It’s not research if you know what you are doing. You are working in unknowable terrain, in a medium of uncertainty, by definition. The important thing is to keep going, to make progress, to put one foot in front of the other. Trust the process.

It might be possible to give more practical advice for clearing all these hurdles. Most of the advice that follows will sound easy but it’s really not. There is no denying, most people will find writing a PhD thesis difficult. This is not entirely surprising and not the candidate’s fault. The PhD is in most countries the highest educational qualification you can get. It better be hard. There are of course easy ways to get a PhD, for one, you can buy it on the black market, but at least in my field actually writing a thesis is not one of these paths. And while you are at it, you might as well be serious about it. It’s a one-time experiment. Why not try as hard as you can. There is in all likelihood not going to be a do-over.

Finding reviewers

To reiterate: A thesis is ultimately tied to the evaluation of peers. Therefore, it is important to find peers, test readers, who are willing to look over the outline, the introduction, a couple of sections, or even the full thesis. All the way. The thesis should not be in a secret drawer until submission date. It needs to circulate among peers, collect feedback, collect coffee stains, and make the rounds. This is hard, because showing your work is always hard.

The peers can be friends, fellow students, postdocs, staff, but they need to be willing to criticise, if possible in a constructive way. Finding people who can do that takes time. It is hard to accept critisicm, but it is easier if it happens early in the process. It is also easier if there is time to build up trust. It is easier if you like that person who wrote with red ball pen all over the carefully crafted chapter. But finding people who you like, who are also willing to criticize you, if necessary harshly, and who you still like after all that, is very hard. This is the conundrum of peer-review — how do you separate your personal relationship with your peers from the criticism you get from these persons? You can’t.

Sometimes commenters contradict each other. This happens all the time. Sometimes they agree. Sometimes a comment is completely incomprehensible. That might indicate that the text it relates to is incomprehensible as well. In any case, it is not the readers job to rewrite the thesis. They just have to comment. The decision is in the hand of the author. Every single word. Many decisions. That’s what makes the author special. Take every single comment seriously for a moment. Think about it. But don’t agonize about it. In the end, it’s all yours.

Learning how to write

Learning how to write is not something that happens over night, at least not typically. Writers write all the time, and when they don’t write, they read (maybe that’s not entirely accurate). A lot of the work of a PhD student has nothing to do with writing, but it is wrong to think that writing only happens at the end. It is important to start writing early. Not the thesis of course, but papers, articles, blogposts. Write early and for diverse audiences. Write a report about your work every week. Show it to other people. This will build confidence, vocabulary, mechanics. It will make writing much easier when the deadline is only a few weeks away.

Apart from writing, the other important practical exercise is reading. Remember, again, that peer-review will decide about your PhD thesis. Therefore, reading peer-reviewed papers is an important path to find out what qualifies as peer-reviewed writing in your field. Read papers and reviews and other people’s thesis. A lot. How many papers do you read or at least skim every month? If the answer is less than ten, you are not doing it right. Some of the papers will be crappy, some will be good, and some people might be able to tell you which is which, if it is not apparent. But it doesn’t matter. Read around your subject. It will help you figuring out how much substance you need in your own thesis. And it might help in establishing a style of academic writing.

All this reading has a desired side effect — it will later help you to derive the factual framework for the introduction and the discussion of your thesis. Knowing the literature is an indispensable part of writing a thesis, in any case. Later, everything you claim that you don’t derive on your own, with your own original data or equations, needs a reference. Everything you don’t want to explain in detail needs a reference. Everything that is not self-contained needs a reference. So, take notes while reading, in some organised manner. You are going to need these notes. Include the links to the papers. References put your thesis in context, they make your thoughts reproducible and therefore useful. References are the ties that embed your thesis into the body of literature. They allow you to stand on the shoulders of giants.

With regards to style, I only want to give one general advice. Keep it simple. Really. The science you are writing about is complicated enough. There is absolutely no need to make it even more complicated through convoluted language, long words, and unnecessary jargon. Use simple words. Write in short sentences. And make the syntax as simple as possible. Academics have the terrible inclination to hide their doubts and fears behind complex language. The jargon is the shield that protects them from confrontation. At the same time, even the most stupid argument can sound incredibly smart when dressed up in convoluted language. Don’t fall into the language trap. If you discover that your sentences are long and convoluted, think through the argument again. If you don’t write in comprehensible sentences chances are that you are not thinking straight. Keep it simple.

People can advise you on what to write. But nobody can tell you how to write. Start planning early, if that is possible. Then find your writing routine. Some people agonize over every sentence, but once they put the sentence down, it is perfect. Others rewrite and rewrite and rewrite. Most agonize AND rewrite. How much can you write every day? Thousand words? How many hours can you write per day and not lose focus? How many weeks do you need for the full thesis? Two months minimum, I would guess. Then revise, rewrite, revise, and rewrite. Over and over again. You are going to hate it at the end. But in a good way.

What environment helps you writing? Do you need silence? What is your preferred writing software? Do you need a specific type of music? Do you need a specific type of coffee? All that is fine. I don’t know many people who can write everywhere, under every circumstance, no matter what. Find a space you feel comfortable in. Find your routine. Most people write in blocks of anything between 10 minutes and two hours. Not many people can really write well for longer. But this doesn’t mean that you can’t do anything else. You can revise and rewrite, revise and rewrite. You can work on references, figures, tables. You can eliminate the one nagging thing you always wanted to check. You can go for a walk, listen to music or play pingpong.

The final stretch

The final months of a PhD scholarship are going to be one of the most intensive periods of time in your entire life — if you allow that to happen. Not only do you agonize over your work, you also need a new job and a new life. You might finally figure out why you hate your supervisor. You might finally put it all together. Money issues are likely. Visa issues might happen. Family and relationships have to be sorted out, in anticipation of the change in circumstances. I have no idea why I am telling you this, because I sure as hell can’t help with any of this. But maybe it is a good idea to get the actual writing out of the way, at least some of it, as soon as possible. To at least maintain the illusion that you are fully in control. That you are swimming instead of drowning. But maybe that is not always possible. It is completely understandable to wait until the very last moment. Most people do and still do not drown.

Finally: A PhD thesis is not the end of the world, nor is it the beginning, although it sometimes feels that way. It can be a means to an end or an end it itself, and only you decide what role the PhD is going to play in your biography. For some it is just a footnote. For others it is really really important. People freak out over it. In any case, it will take up years of your life and at the end you hold this book in your hand. All your unfinished thoughts, your ideas, your projects, the uncertainty, the struggle, all this is now in this heavy book that you hold in your hand. A finished product. It is so weird. And it is fantastic.

Some literature for further reading

On writing:

Steven Pinker: The Sense of Style: The Thinking Person’s Guide to Writing in the 21st Century. very short summary on Wikipedia

Psychology/procrastination:

Neil Fiore: The Now Habit: A Strategic Program for Overcoming Procrastination and Enjoying Guilt-free Play
(Students who spend all waking hours working on their PhD theses actually finish later, so make sure you allocate a lot of time for other activities. Fiore recommends using an “unplanner”.)

Unavailable in English, but for those who read German, French, Italian, Finnish, Czech, or Korean: Kathrin Passig / Sascha Lobo “Dinge geregelt kriegen — ohne einen Funken Selbstdisziplin”
(Two sentences summary: Procrastination is good for you, there’s no need to reform your personality. Learn how to procrastinate professionally and you’ll be fine.)

John Perry: The Art of Procrastination: A Guide to Effective Dawdling, Lollygagging and Postponing
(Here is a very short version of his argument.)

Wikipedia: Impostor Syndrome
Almost everyone believes they’re merely faking it. And maybe they are. In any case, it’s not just you.