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It is possible to obtain two PhD degrees (various fields) on the basis of one interdisciplinary PhD dissertation? Is this something feasible (in Europe)?

Or maybe there must be two different 'physical' doctoral dissertations?

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    Usually not, because it's forbidden to defend the same thesis twice. – Trilarion Mar 10 '18 at 13:18
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    Why would you want to? It seems like a waste of energy to me. A research degree is a paper saying that a department at a university judges you able to do independent research on a scientific level. Why would you want two of those? – mathreadler Mar 10 '18 at 15:25
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    @mathreadler A PhD in a particular field is often taken to be a strong qualification of one's expertise in that field. It's not strictly necessary to have multiple PhD's to be have cross-disciplinary credibility, though it certainly could be helpful. – Nat Mar 10 '18 at 19:15
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    @Nat I don't think so. Most people would be puzzled why you'd even think of doing it. I think many people would be curious to ask "So why did you go for a second PhD? Could you not find any post doc spot or assistant professor spot, or job in industry..?". – mathreadler Mar 10 '18 at 23:19
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    I have seen this happen, with multiple cases of the same student earning PhDs from different departments (somewhat related topic areas) at the same top university. One department required a private defense and the other, a public defense, so I think there were two defenses. For privacy reasons, I can't name names. – WBT Mar 11 '18 at 18:23
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No, at least the regulations that I am aware of require that the dissertation be a novel contribution to the respective field and that it has not been submitted before.

If you write a dissertation at the crossroads of different fields, you have to decide for a field in which you want to formally graduate and obtain a degree. It may be advisable to look for supervisors from different fields or with an interdisciplinary background.

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    Would this still hold if submitted in different countries? What do you think personally? – SK19 Mar 10 '18 at 10:43
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    @SK19 yes, it does. – henning -- reinstate Monica Mar 10 '18 at 10:46
  • Or, alternately, find one of many interdisciplinary PhD programs. – Fomite Mar 11 '18 at 6:10
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    @SK19: A (state of the art in a given) field does not end at national borders. – O. R. Mapper Mar 11 '18 at 14:47
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It's hard to imagine any legitimate university allowing a thesis that has already been submitted for some other degree, whether at that university or somewhere else.* If you lied and claimed it was a new thesis, your degree would be revoked if they ever found out. Furthermore, there are more requirements to earning a PhD than just presenting a dissertation. You're not going to be able to register as a student and submit a pre-prepared dissertation the next day.

And, anyway, what's the point? A PhD is generally treated as a level of achievement, rather than a quantity of achievement. Getting two PhDs is like getting two driving licenses. That doesn't show you're twice as good a driver – it's just saying "I can drive" twice. Why would you want to prove twice that you're at the same level, instead of using all that time to advance beyond the level of being a grad student?

Having two PhDs is so unusual that everybody is going to ask you about both of them. How impressed do you think they'll be when you admit that this second PhD you were bragging about was just the resubmission of the same dissertation to another university?


 * And note that la femme cosmique's answer is a case of the same thesis being simultaneously submitted to two universities as part of a joint programme that both universities agree to when the student enrolled.

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    Getting two PhDs is like having two driving licenses. I have to remember that one. – henning -- reinstate Monica Mar 10 '18 at 13:06
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    Some universities allow this. I have a friend who did 2 years of his PhD in France and 1 year in China. He now holds, at completion, a PhD from the French institution and a PhD from the Chinese one, from one thesis (although separately in English and Chinese). But it's still the same field. Semi-related. OP could find a 'co-tutuelle'-ish arrangement between two institutions/groups in different fields in which this is theoretically possible, but that would be a pre-established relationship rather than something to do during the PhD. – la femme cosmique Mar 10 '18 at 13:10
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    @lafemmecosmique That's interesting to know. I think it would make a good answer. – David Richerby Mar 10 '18 at 13:18
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    I have two driving licenses -- one for the left and one for the right. :P – Thomas supports Monica Mar 10 '18 at 23:26
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    Well, I finished one PhD in chemistry, but thinking to take one in humanities/social science, I am stupid for dooing it? – SSimon Mar 11 '18 at 14:46
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It is possible to do this, but usually the arrangements are pre-designated before you do the PhD. My answer is going to be very specific here; I have a friend who did this, and I know it's "a thing" at least in France. But as I said, the scope of the answer is therefore limited to a PhD done jointly between a French lab and one somewhere else.

A friend of mine has done a "co-tutelle internationale de these" which means that he spent 1 year of his PhD in his home country (China) and 2 years in a lab in France (paid by the Chinese government). At the end he wrote his thesis in Chinese and again in English (with a French abstract), defended in China, and he has two PhDs; one from the home institution and one from the French one. These agreements are somewhat common, at least in France, although I cannot really speak for other countries. However, that does mean that it is theoretically possible. As far as I'm aware, besides the language, the theses he submitted were the same.

It is not difficult to imagine a situation in which one of the labs is a different discipline to another (e.g. something like engineering vs. astrophysics) and so you could end up with 2 PhDs in such an arrangement. However these things are pre-arranged before the start of the PhD, and to form a new one would probably be a lot of administrative work.

However, it's possible, at least here.

Some stuff about it is written here:

https://ressources.campusfrance.org/catalogues_recherche/diplomes/fr/cotutelle_fr.pdf

Especially the paragraph that I'll poorly translate:

Which degree do we obtain?

Each cotutelle thesis is held within the framework of a convention linking two institutions of which one is necessarily French. The procedures and rules are those of the French doctorate and those of the doctorate in the partner country. The two universities recognize the validity of the cotutelle set up and that of the degree supported (grade of Doctor for French university and equivalent diploma for foreign university).

Concerning the issue of the diploma, there are 2 possibilities:

• The student receives a Doctor's degree conferred jointly by both institutions. The diploma is mentioned under his two appellations (for example: PhD in French literature and PhD in French literature).

• The student receives two doctoral degrees from each institution. Each diploma then bears the mention of the diploma specific to each institution, mentions the fact that the thesis was made in co-supervision and specifies the name of the partner institution.

In both cases, the thesis is defended in only one of the two institutions associated with the cotutelle, by decision of the two research directors.

But this is a highly-specific answer which is France-centric. Is that possible elsewhere? Probably. But I don't know enough about it to answer.

  • Yes, it's possible elsewhere, see also this answer of mine. I know of different cases, e.g. Italy/France (a student of mine who graduated last year), Italy/Germany and Italy/Finland. – Massimo Ortolano Mar 11 '18 at 15:18
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    I wonder how much these dual degree programs are really just the result of (or vestiges of, in the case of a post-Bologna Europe) bureaucratic headaches that people have to have their degrees recognized in different countries. I'm not aware of any of these programs being within the same country (unless one is a professional degree, e.g., MD/PhD at Emory / Georgia Tech) – user0721090601 Mar 11 '18 at 16:04
  • @guifa knowing French administration, this would not surprise me in the least ;) – la femme cosmique Mar 11 '18 at 16:31
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It depends on what you mean by two PhD degrees. The University of Michigan allows dual PhD degrees, for example in Physics (or a bunch of other subjects) and Scientific Computing. There is no possibility for a stand-alone degree in the latter but after you fulfill certain requirements, you get a PhD in Your-Subject and Scientific Computing. The requirements comprise a certain units of classes and that the student "make extensive use of large-scale computation, computational methods, or algorithms for advanced computer architectures in their doctoral studies".

  • I will add to this that the University of Michigan also allows for what they call a "Student Initiated Doctoral Program" -- essentially a "double-major" at the doctoral level. My own degree, for example, was in "Mathematics and Education", and was awarded by both the Dept. of Mathematics and the School of Education. – mweiss Mar 11 '18 at 1:45
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    What you're describing sounds like it's still just one PhD degree, only that the subject of the PhD happens to be cross-departmental. I don't think it makes sense to offer this as an answer to the question. – David Z Mar 11 '18 at 5:35
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    As @David Z says, this is probably a single PhD in Physics and Computing, not one PhD in Physics and another one in Computing. Can you clarify? – henning -- reinstate Monica Mar 11 '18 at 10:39
  • I cannot speak with confidence about @tripathea's answer, but regarding my comment, yes: it is a single PhD awarded by two departments on the basis of a single cross-disciplinary dissertation. That is possibly the closest approximation to what the OP asks for. – mweiss Mar 12 '18 at 2:05

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