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I've often read that having more than one PhD is badly seen. Is there a good reason for this? Good obviously means with some kind of evidence to back it up beyond plain and simple "personal experience" and opinion.

I've seen many comments about this matter, but often rely on a kind of judgment that sounds highly personal and by no means endowed with the academic objectity that I would expect.

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    Did you check the answers on "multiple PhD" on this site? They will most likely answer your question, although indirectly. You can use the search box on top of this page. – henning May 21 '18 at 13:45
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    I'm not sure I believe the premise of this question. There are several answers on this site suggesting it's not generally a good idea to pursue multiple PhDs, but that's different from suggesting that already having multiple PhDs is viewed badly. In any case, I think that among those earlier posts, this answer may come closest to addressing your question: academia.stackexchange.com/questions/17232/… – Mark Meckes May 21 '18 at 14:38
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    One thing to keep in mind is that a PhD is not a medal showing to the world how smart you are. Rather, it's an apprenticeship for becoming a researcher. Having multiple PhDs to show that you're qualified is closely analogous to trying to become an exceptionally skilled electrician by going through trade school multiple times. – Kevin May 21 '18 at 17:26
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    It's certainly not frowned upon in Hollywood! (sarcasm intended) Many times I've seen (in a movie, in a TV series show, etc.) a certain character's super-dooper scientific credentials established by mentioning the several Ph.D.'s he or she has. – Dave L Renfro May 21 '18 at 18:02
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    As David Richerby said: "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." – henning May 22 '18 at 14:39
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I think your assertion really is an overgeneralization, but there are some negative points to pursuing more than one PhD.

It's the same concern as it would be for pouring an inordinate amount of resources into the wrong pursuit. It might indicate something about the recipients decision-making abilities, or "perpetual student syndrome".

That said, if that's what one needs to do to pursue the career one wants, that's what one needs to do.

Let's look at two distinct situations. A college junior starts thinking about her career path, and thinks"

I want a very specific, highly specialized pursuit. I believe that I will need two PhD's to establish my credibility and skill set for this path. I am setting out to get two PhD's, and have a good plan for doing so. I've already considered whether I can acquire the skills and knowledge by doing one PhD, and then endeavoring to cover the shortfall by some other means, and I don't think I can. I'm well aware that some of the skills I learn during one PhD will be redundant with what I learn in the second, but there's absolutely no way around it.

Contrast this with a senior, who doesn't manage to get a job, so enters graduate school -- gets one PhD, doesn't see the career prospects, then gets another PhD to fix things.

Clearly, the first situation is better (though, I'd argue, exceedingly rare, and often unnecessary). The second situation is much more problematic, likely more common than the first, and arguably, what some people tend to think the path was when told someone has two PhDs.

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    I'm having a really hard time identifying a career path that requires two formal PhD's, unless one discipline is in the humanities and the other is in a STEM field, and one decided to start with the non-STEM field. – aeismail May 21 '18 at 14:16
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    @aeismail -- yes, "exceedingly rare" – Scott Seidman May 21 '18 at 14:18
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    @aeismail Some people in philosophy of science do it that way. Massimo Pigliucci got first a PhD in biology, then philosophy (in his 40s or so). – M.S May 21 '18 at 16:35
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    I do not know of anybody in the first cohort, and have very hard times figuring the scenario. We seem to agree and have experience of the second instance. I do praise that kind of second PhD. That tells me of extreme passion for academic, of interdisciplinarità, of resilience and dedication in face of low pay and hard work. I know of one physicist retrained as economist and now professor. – famargar May 21 '18 at 19:34
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    @aeismail Maybe not exactly two PhDs, but MD + PhD is extremely common and JD + PhD is quite common too. – Elizabeth Henning May 21 '18 at 20:25
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First of all, it’s not clear what you mean by “badly seen” and whether (or to what extent) your premise is correct. But to the extent that it is badly seen, I would argue that it has to do with efficient use of resources. If you think of your intellect as a resource, the general recipe for making the best use of this resource is:

  1. Spend a few years developing your intellect by getting an education. This doesn’t produce an immediate “output” but is an investment (quite a costly one in fact) in the future.
  2. Spend the remaining 30-40 years of your career working. What you produce during that time is the productive output that benefits you and the rest of society.

Most people who get a bachelor’s degree spend 3-4 years on stage 1. People who get a PhD invest another 4-5 years, and this is seen as justified (mostly!) thanks to the very specialized skills a PhD helps them acquire. However, when someone gets a second PhD they extend the unproductive period of stage 1 to a total of something like 12-15 years, taking away valuable productive time from stage 2. The added benefit in terms of specialized interdisciplinary knowledge that they acquire would in most cases not be enough to justify such a large investment. 99.99% of people simply do not need two PhDs to fulfill their potential in life. Even from the purely intellectual point of view of a person who is very curious and passionate about learning two subjects in depth, the first PhD already teaches them to be an independent researcher, which would enable them to get the knowledge they would pick up in the second PhD in a fraction of the time and effort that a formal PhD program typically requires.

Getting two PhDs might make practical sense for someone who decided on a drastic career change after their first PhD and want to go into a different profession where a PhD is a requirement.

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    True, but compare: a neurosurgeon spends up to 12 years (med school plus training) to be qualified, and nobody whines about the "nonproductive years spent." I think part of the problem is that PhDs nowadays require less work and a less rigorous thesis than a MA/MS did 50 years ago. – Carl Witthoft May 22 '18 at 15:17
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    @CarlWitthoft it’s not clear to me what can be learned from this comparison. I don’t know anything about neurosurgery but I would think that during much of the 12 year period you are describing, neurosurgeon trainees are already highly qualified doctors and are engaged in productive activities (working at a hospital and treating patients). Perhaps that explains why “nobody whines” about them. – Dan Romik May 22 '18 at 15:31
  • @CarlWitthoft I take it to be a problem that many universities don't require a masters degree to enter a phd program. This has lowered the standards greatly. – M.S May 23 '18 at 10:58
14

I think you misunderstand the purpose of a PhD.

A PhD does not establish you as an expert in a field. Rather, it is the minimum entry criteria for a career in research. The main focus of a PhD is actually preparing you for a career in research. The secondary focus is deepening your knowledge in a particular subject area.

While there are obvious exceptions to this, your research as a doctoral student is unlikely to have any lasting impact or even to be strongly related to the areas where you focus on after receiving your PhD.

In this context, there is very little to gain and much to lose from spending several years pursuing a second PhD. What you may gain is a deeper understanding of a second field. However, this will come at the expense of reverting to being a student and missing out on opportunities to build your career. You will also have to repeat a significant amount of effort that again is unlikely to be related to actual work once you move beyond being a student.

  • "it is the minimum entry criteria for a career in research" Then multiple PhD should be required to perform interdisciplinary research, since the person who has a PhD in a field, doesn't satisfy the minimum entry criteria for research in different topic. – M.S May 23 '18 at 10:56
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    @M.S It's not the minimum entry criteria to do research in a specific field, just the minimum entry criteria to do research in general. Think of a PhD more like a high school diploma for those wishing to do research. You need one to check a box on application forms, but having more than one wouldn't help you. – Eric May 23 '18 at 11:24
  • @M.S To clarify further, it's not that having a PhD in say biology immediately qualifies you to do research in astronomy, but you'll get there faster with better longer term results by following the traditional approach rather than starting over pursuing a second PhD in astronomy. That is, identify areas for joint research with your secondary field, do joint research with collaborators in that field and work gradually towards doing the multi-disciplinary research or doing research directly in your secondary field. – Eric May 23 '18 at 13:25
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There are a few possible reasons what HR/Hiring mangagers would not like to see this.

  • If you follow a Phd and then a second Phd (before you obtain a permanent position, job or retire), it sounds a lot like you really want to go into research but something went wrong with your first Phd.

  • At the same time when you finish your second Phd, other applicants already have a few years of Job experience, while a second Phd more often than not doesn't add a big environment change

  • It may appear to some people that you lack focus.

  • Your hiring manager may lack self-esteem

  • You are supposed to be "too academic"

  • People may think you look down on other people

5

I don't see the general problem with a second doctorate.

If you want to make a streamlined carreer into management or faculty, don't do it.

If you need (or want) to be settled in a permanent position by the age of 32 for financial reasons (family etc), don't do it.

But if you have the means and guts, if you really still want the second one after you've defended the first, why not? You might loose points with a few brainless HR people who think the apt treatment for kinks in a CV is the same as for wrinkles in a shirt, ironing them out. But who cares? That company is for the dogs anyway.

  • "f you want to make a streamlined carreer into management or faculty, don't do it. If you need (or want) to be settled in a permanent position by the age of 32 for financial reasons (family etc), don't do it." Why would any of those occur? – M.S May 21 '18 at 20:59
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    @M.S Very reasonable goals imho. No? – Karl May 21 '18 at 21:02
1

I will shortly complete a second PhD in a related, but distinct, field. In essence, the second study has been more akin to post doctoral work (but with an added degree) - I have had to undergo no training, my tutorials are virtually non-existent, and the resultant second thesis has already been accepted as a book. As with the first, I expect to complete with, at most, minor corrections. Both PhDs have been 100,000 words and both completed within 5 years (part-time) - thus 2.5FTE. Before the cynics comment - both have been/are being attained at universities ranked within the world top 100. I agree that there is a problem with people being non-productive for 10+ years - the answer is to work harder in the evenings and to ensure that PhDs are completed on time. Though hardwork, it does enable me to now more readily apply for inter-disciplinary work and the fields of employment have doubled.

1

I think it is frowned on as excessive investment and limited return. There is a ratio that Stephen Covey talks about (horrors a business book writer!) with the amount of effort spent in learning versus production. In a way, a Ph.D. is already a bit of an indulgence. Doing two of them sounds like you just like being in school all the time, versus being a PI.

In most fields, about 75% of the Ph.D. is research, not learning. So if you just wanted to LEARN many fields, you should pick up multiple masters or even multiple bachelors. Of course, you ought to be independently wealthy to allow that.

Doing multiple Ph.D.s feels a bit as if you are just collecting tickets without thinking of the meaning of them. I mean once I had DONE a Ph.D., I really felt like I didn't need the sheepskin to contribute. Or at least part way through, it "clicked" and I got it and was an independent researcher. I was a little older so it was easier for me (to draw on practical experience). But even the "straight out of bachelors" clicked by the end of the Ph.D. They could write their own papers, determine their own experiments, negotiate with vendors to buy apparatus, etc. etc. Doing two would make no sense, since you've already got the "I can figure it out" gene turned on in your codex.

P.s. I agree with the comment that says you don't indicate having read the responses already on this site to this issue. This is not a good trait...

0

I don't think it is frowned upon to have multiple PhDs.

However, it is definitely rare to meet a person who has multiple PhDs. Anecdotally, I would estimate that fewer than 1% of people with a PhD will have a second PhD.

I know of only one person from my social circle who has a second PhD:

Dr. Ye Lu received a PhD in operations research from MIT in 2009, a PhD in mathematics from the University of Notre Dame in 2006 and a Bachelor of Science degree in applied math from Tsinghua University in 2002.

In my opinion, it made sense for him to get a second PhD because it allowed him to get a tenure-track academic job in Operations Research, whereas it is much more difficult to get a tenure-track academic job in Mathematics.

In conclusion, it can make sense for you to get a second PhD, but it depends very much on the particulars of your own circumstances.

  • I'm guessing Dr Lu is chasing a 'brand name' on his/her CV. – Prof. Santa Claus Jul 12 at 0:16
  • @Prof.SantaClaus I disagree. Notice that his second PhD was in a related but different field of study. I think that the main benefit was that he could get an academic job in a field where getting an academic job was relatively easier. – I Like to Code Jul 12 at 2:08

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