How important is the Ph.D. Thesis?

Question

It may sound an insincere question but bear with me, please.

I am just starting to write my thesis. I got some good publications along the way, and I have a couple under review which I hope will get accepted in tier 1 journals. So the question is, does the thesis in itself add a lot of value to my Ph.D.? Or is it necessary just as part of the formalities?

Also, two related questions are

• How do the thesis reviewers' expectation/judgement differ from the journal reviewers' expectation? Obviously, it is the same people usually. But when you (as a faculty) review a thesis, do you look for the same elements as when you review for a Tier I journal?
• If the candidate has good publications, does that make you, in want of a better word, go somewhat easy on the thesis?

My professor is, of course, not letting me take it somewhat lightly. I understand where is he coming from since his colleagues will ultimately examine the thesis. But off the record, how critical is the thesis for my career after the defence is over?

Answer 1

How important is the Ph.D. Thesis?

It depends on what you have in mind for "importance". The intellectual content of the thesis is vitally important, since it stands for what you have accomplished in graduate school. You should make sure it contains your best work, since early in your career you'll be judged partly on this basis.

In the long run, there is little direct value to the dissertation as a document. (Aside from any sentimental value, laying out the historical record, and satisfying bureaucratic requirements.) Any valuable content should be published, and the resulting publications will be the definitive source that the community will rely on in the future. If people are still reading your thesis five years after your graduate, then that's a sign that you have not done an adequate job of publishing your work.

Opinions differ on how seriously to take the dissertation as a specialized form of academic writing. For example, how much additional background, commentary, or literature review should it contain? Should it be written in a different style from published papers? This can vary between countries, fields, universities, departments, and even individual advisors. There's no universal answer, and you'll have to investigate what fits your particular circumstances.

In particular, one fundamental question is whether your dissertation is nothing more than an account of research that has been or will be published, or whether it's an important academic exercise in which you demonstrate your perspective and thoroughness in a way that would not fit in a conventional paper.

I see the former as the default answer for mathematics in the U.S., but the latter is not completely unknown. (There are advisors who insist that their students write far more detailed proofs in the dissertation than one would ever actually publish, to demonstrate that the student can in fact do this.)

Answer 2

The importance of a person's Ph.D. thesis per se for their further academic career varies wildly, because the thesis is just one component in a person's portfolio. The significance of that component depends strongly on their intended direction and the contents of the rest of the portfolio.

First and foremost, remember that most people who obtain a Ph.D. do not end up becoming faculty at a top-tier research university. If your ambition is to end up in a more teaching-centric position or in industry, then research work is mostly just evidence of one's necessary technical competence. The primary work that such a person is hired for is almost never directly linked to their thesis: in a teaching post you may continue that research, but that is secondary to teaching; in industry you are probably going to end up working on something different, but that will exercise similar technical skills.

Even for those who do aim for a career of self-directed research (e.g., tenure track faculty), however, the thesis is only one part of the more general research portfolio. In some fields or for some particular people, the thesis is the key point of contribution, standing above all of one's other work. For many others, however, either the thesis is a compilation of results that have been achieved and published along the way, or the thesis is only one piece of a greater body of work. It is often the most important because others may have the person as a secondary contributor, but across all fields it is rarely the only significant piece of work.

Moreover, the next step after a Ph.D. is typically not faculty but postdoc, and it is one's ability to "flower" and become well published as a postdoc, with more self-direction and outside of your home laboratory, that is often a much stronger determinant of faculty hiring.

Now, if you write a bad thesis, it will most certainly be a detraction. In general, however, I would say that for most people in many fields, the Ph.D. thesis should be viewed as having an importance only equivalent to 2-4 major papers.