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This might be a bit of an abstract question, but what defines a dissertation? Some colleagues and myself have been debating this and some are arguing that three peer-reviewed publications or a long monograph make a dissertation. However, others are arguing that the dissertation is defined not by the length or number of publications, but the significance of the contribution. Is there any scholarly consensus on this, or is this a continuing discussion in academia?

Don't have a source, and things may be different in different parts of the world, but I've always considered a dissertation to be:

A long monograph submitted in partial completion of the requirements for a PhD

• Dissertations are generally submitted by grad students as they complete their PhDs -- other academics might publish long monographs, but that wouldn't be considered a dissertation.


• Certainly I don't think there is a well-defined standard for how significant a contribution has to be to merit a dissertation -- it's whatever the committee will accept (though in principle, it should have some new advance, not merely a survey or report).


• Some institutions may allow you to staple together your papers to produce a dissertation; most require a separate document that re-hashes work that may (or may not) have been published elsewhere.

This depends on field and on location. In mathematics, generally, if not universally, a dissertation is a significant contribution advancing mathematics in a subfield, where significance is judged by an advisor and a committee. It doesn't need to be published at all, though the candidate may have one or more papers based on it.

In other fields, a "dissertation" is, as you suggest, just a collection of published papers, where the quality is left, perhaps, to the editors and reviewers. It might even be a single publication.

A dissertation could be long or short, but its length has nothing to do with its quality. A three line proof that P = NP would, in CS, if correct, be a monumental contribution.

There isn't really a discussion "in Academia" though there might be within some fields or at some universities. A new field, in particular, might go through a period of uncertainty as to what should be generally accepted within that field. Most likely it would settle out somehow within a few years.

In those fields in which advisors/supervisors play an important part, it is the definition of the supervisor that weighs the most.

It would be more interesting to talk about what a dissertation ought to be. I have always been against the (rather modern) convention of a candidate stapling together 5 published papers and calling it a dissertation. If one is to really be a Doctor of Philosophy, then he should really understand the philosophy of his field and his dissertation should show it.

You published 5 papers, two of which were "monumental" and all in highly respected journals? Swell. That shows that your advisor can hand you problems and you can solve them (or hand you topics and you can research and write interesting things about them.) But is doesn't show that you know what an interesting problem or topic is. Sure, you can get an assistant professorship and then work in a research group at a flagship university, but still, it's the PI handing you problems which you solve.

But how to your papers fit into the larger body of knowledge? What makes them useful and interesting? Where are these topics going to lead? Those are higher-level questions, and I think the dissertation should not only be a publishable result, but also should show the world why the result should be published (and funded and pursued further.)

I speculate that the pressure (which I believe began with the Viet Nam war college deferment) to produce a lot more Ph.D.'s has caused academia to loosen the standards for who gets to be a Doctor of Philosophy. We now have about 3 times the number of Ph.D.'s that society really needs and most of them are just grinding out papers that no one really cares about.

So my opinion is that a dissertation is a publishable result wrapped in a good thick layer of why it's a publishable result.

Obviously there is not a consensus, given the differences in practice. Even if debating this, I don't think there is an easy answer and you will get different points of view (different pluses and minuses and tradeoffs).

I tend to the view (in the sciences) that the dissertation is just a hurdle to get out of the way, but much less important in learning or in contribution than what you did in publications. I think a gentle stitching together of previously done papers along with a perfunctory intro and background is fine. (Perfunctory because I think a thorough review makes more sense when a senior scientist.) The main disadvantage to spending too much time or effort on the thesis is that it either keeps you longer or it takes away from lab work and real papers. Time is not infinite.

In general, I think most students would be better advised to try to get through the thesis fast AND to look at it somewhat cynically as a pass/fail school exercise. In other words, NOT like writing the King James Bible. On the other hand, your papers ought to be very well honed little gemstones. They are going into the archived literature (so is the thesis, but nobody looks at it.) This might be very different for someone in the humanities where writing a monograph is an important skill. But we need to be realistic that somebody working on helium-3 is getting a doctorate in condensed matter physics, not "philosophy" (despite the confusing term "Ph.D.")

I do like the use of the dissertation to be able to include results not yet published (but then please try to get the chapters converted later...nobody reads dissertations like they read papers). In addition, you can include a little more work that does not fit well into regular papers (failed experiments, etc.) The rationale is that at least you are getting it published somewhere. But still better in articles if possible.

In addition, you can go more into details on future work ideas, innovations in lab technique or tools, or practical advice on benefits of different methods. Follow-on students in the lab group can benefit from this and are a likely audience to read the dissertation.