All this depends on the field, the country, etc. but in theory, if you already have a master's degree, it is possible to get a PhD based on previous (published) research. But typically not on a single paper. (Over)generalizing and assuming your research is genuinely interesting and meets all the (sometimes arbitrary) requirements of your field, a rough guideline is that you need material corresponding to at least three papers.
You would also need to write some intro/conclusion putting the research in context, make revisions based on your advisors' comments, find a jury and satisfy them. You cannot just show up with a paper and “wish” for a PhD, at least not from a real, reputable university. That's assuming you really manage to make your research publication-worthy (which means not only rigorous but also connected to recent literature and current problems in your field) and find a faculty willing to accommodate you as it's not the “normal” way to get a PhD.
Don't overlook the bit about finding an advisor: It's incredibly important. The PhD is really an apprenticeship under the supervision of a full professor. You don't ask a university or department for a doctorate, there is no process to submit a thesis and have it evaluated on your own, it's all driven by faculty members and you won't even be allowed to defend a thesis if it's not endorsed by one (he or she would also typically help you recruit a jury).
Realistically, a mediocre thesis can be validated if a professor puts his or her mind to it, asks friends to sit in the jury, etc. but even brilliant work is nothing if you don't find an interested academic to move the process along.
Beyond that, others have mentioned extra requirements but the thesis is really the most important thing. In my experience, in Europe (I got my PhD in the Netherlands but I know a little bit about France, Germany, or the UK), it's increasingly common to organise some mandatory courses for PhD candidates but the load is very light, a few short courses about soft skills or methodology with no exam, only pass/fail based on attendance. And there are ways around that if you have a good reason.
But to be perfectly honest, your question suggests you are not very familiar with academia so it seems highly unlikely you would succeed in getting a PhD without proper support. I am not sure why you want one but if it's important to you, it might be a better idea to simply enroll in a PhD program.
Last month, we offered suggestions on how to prepare for your thesis defence: Decide whether you need more research results, sketch out a plan for those experiments and for writing thesis chapters, and--importantly--get your supervisor's support for that plan. Now it's time to wrap things up in the lab and start writing.
Writing a thesis is easier said than done, of course, and you have plenty of work ahead. But like any big undertaking, writing a thesis is easier if you break it down into smaller steps.
First things first
If you haven't already made a countdown plan as described in last month's column, start with that first. Then, before you start writing, make sure you and your supervisor agree on the table of contents. This might seem obvious, but we have seen too many students start working on chapters only to have those chapters tossed out later.
Cut the problem down to size
Once you've decided on a table of contents, it's time to expand it into a detailed outline. Your outline will be several pages long and consist of chapter headings, subheadings, figure and table titles, some key words, and essential comments. Your outline will keep you on track and provide you with a framework for the text. It also forces you to break up the writing into manageable pieces.
Determine the format
Your department or university may have a standard format for your thesis. If so, there's probably a standard template you should use. If not, save yourself frustration and time by copying the format from a thesis that appeals to you. Make sure the format or template is easy to use. Once you've sent your thesis to your committee for review, you may consider upgrading your layout. For now, factor the format into your plan, but don't make it your primary concern.
While we're on the subject of format, be sure to use the proper citation format for your list of references. This list can run into the hundreds, so use the approved format for citing literature from the very beginning--both in the text and for the list of the references at the end. Use a good citation-manager program and enter all the information for every article referenced--including titles. You won't want to have to go back and redo this if you've done it wrong!
Transform published articles into thesis chapters
Before you delve into the chapters you have to write from scratch, start by transforming your published articles and submitted manuscripts into thesis chapters. It's not just a matter of stapling your papers together and sticking them into your thesis, however. You'll need to break the publications into pieces and weave them into a cohesive narrative, making sure the various parts fit together nicely without redundancies or gaps in logic. When doing this, keep the following in mind:
Drastically cut back or rewrite the introduction section of each article. There is no need to repeat what you will have already explained in the general introduction and literature survey of your thesis. Don't just delete those introductions, however; parts of your manuscript intros will be useful for your thesis introduction, so paste any relevant text into the intro section of your thesis outline for later editing.
Cut the Materials and Methods section as necessary to avoid repetition with other chapters. Again, you'll probably want to paste some of the Materials and Methods text into the relevant sections in your thesis.
Include text that may have been cut from the final version of the article due to space restrictions.
Update your literature citations (see above).
If someone else wrote one of your publications (i.e., you did the experiments but a more senior person wrote the manuscript), we suggest you rewrite the bulk of the text in your own words. Even if experiments were done in collaboration, a thesis has only one author--you--and the words in it should be yours.
After you've transformed your published articles into chapters, you will have to write new material for the remaining chapters. When you first start writing, it helps to begin with an easy section. This will give you confidence and get you into the writing habit. Because the methodology chapter is relatively straightforward, you might want to start with that one. If you've already written several methodology sections for your peer-reviewed articles, it won't take much time to prepare a first draft for your thesis.
Because a thesis has fewer space restrictions, you should take the opportunity to describe the details of your work that did not make it into published articles. In a thesis, it is better to err on the side of being too detailed than to risk leaving out crucial information. Be generous to the next generation of researchers; a detailed description of your progress and failures will save them a lot of time.
Writing up that last set of experiments
Now that you have worked your way through the initial chapters and have written most of your thesis, it is time to tackle writing up your final project. You probably haven't written an article on this research yet, so you'll need to decide whether to write the article first and then transform it into a chapter or do it the other way around.
If there is stiff competition in your field, your supervisor will probably insist that you write the article first. Otherwise, we suggest that you write the chapter first, as this approach will allow you to describe your work in detail. While the thesis is out for review with your dissertation committee, you can select the appropriate parts from the chapter and transform it into an article to submit to a peer-reviewed journal.
10 Tips for a Stress-Free Thesis
The introduction: The final hurdle
Although it comes first, the introduction will probably be the last chapter you write. The introduction is where you need to place your work in a broader context, explaining why the research is relevant to the scientific community and (assuming it is) to society.
Start thinking about your introduction long before you start writing your thesis. During your final year--or even earlier--create a file in which you collect ideas and article clippings that could be useful for the introduction. A file of good ideas will be a big help in writing a comprehensive and elegant introduction when the pressure is on.
The summary is the one section of your thesis that is sure to be read widely. In a few pages you will have to describe the main findings of your thesis research, so it is best to write this part after you have finished all the other chapters. Do not try to describe all your results in the summary--you're simply summarizing the bulk of your work. Be sure to designate in the summary which chapters contain particular findings.
Safeguard your work
We shouldn't have to remind you to back up your work, but we will anyway. Keep a copy of your thesis on an external hard drive, memory stick, or some other storage device. Back up daily and keep the copy (or copies) in a safe place. For extra security, keep a copy of your work-in-progress off-site on a remote server (in the event of fire or theft). The simplest way to do this is to open a Web-based e-mail account and regularly e-mail your work to yourself. There are also companies that offer online document-storage services.
Going for gold: Writing an error-free thesis
Because a thesis is usually written under severe time constraints, it is difficult to produce one without some typos and other minor errors. Spell checkers help, but they can't catch errors in those hard-to-spell technical terms. In addition, errors of grammar and syntax are not always highlighted, and minor scientific errors can be easily overlooked. Your goal, of course, is to have as few errors as possible.
We suggest you do two things to help make this a reality. First, put the manuscript aside for a short while after you've written the first draft. Once you've gained some distance from the material, read it over again with a sharp eye--not for content, but as a proofreader looking for typographical errors. Second, give a copy of your thesis to one or two trusted peers to read. Devise a creative way to reward them for every error they find (free cups of coffee or beer, or pizza, for example). This will give them an incentive to go through your thesis with a fine-toothed comb. If you can afford it, you may even consider hiring a professional copy editor to do this for you.
Most importantly, while writing your thesis, be sure to take care of yourself. Eat well, exercise, and get plenty of sleep so you're at your best when you sit down every day to write. This is the home stretch of your Ph.D., and you want to make sure you cross the finish line energized and ready for the next step.
Patricia Gosling and Bart Noordam are the authors of Mastering Your Ph.D.: Survival and Success in the Doctoral Years and Beyond (Springer, 2006). Gosling is a senior medical writer at Novartis Vaccines and Diagnostics in Germany and freelance science writer. Noordam is a professor of physics at the University of Amsterdam, the Netherlands, and director of a regional audit organization. He has also worked for McKinsey and Co.
Images. Top: Paul Worthington. Middle: courtesy, Springer.
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Patricia Gosling is a coauthor of Mastering Your Ph.D.: Survival and Success in the Doctoral Years and Beyond (Springer, 2006). Gosling is a senior medical writer at CMPMedica in Malaysia and a freelance science writer.
Bart Noordam is a coauthor of Mastering Your Ph.D.: Survival and Success in the Doctoral Years and Beyond (Springer, 2006). He is a professor of physics at the University of Amsterdam, the Netherlands, and director of a regional audit organization. He has also worked for McKinsey & Co.