Few days back while attending a thesis defense, one Professor was asking the defender why does he think, he deserves the degree. I was wondering since then, is there really any general answer for that? or the answer should be given describing my own work and then emphasis them how it is important for research field?
I asked the question here to know your opinion about it and to list down what could be the possible answers to this question.
For a Ph.D., my favorite explanation is this cartoon by Matt Might.
In short: a Ph.D. is a measurable contribution to a sum of human knowledge.
To be able to answer this question, all you need is an idea of how to describe what you have discovered, and how it fits into the context of work by others that has come before. This is often not easy to answer, but an important thing to think about as one is writing one's thesis in any case.
Usually the answer to this is formulated in the rules of the institution. In Germany we call this the "Bachelor-/Masterprüfungsordnung" (for BSc and Msc) or "Promotionsordnung" (for a PhD).
The one from my institution contains something like
Die Promotion dient dem Nachweis der Befähigung zu vertiefter selbständiger wissenschaftlicher Arbeit.
which translates roughly to
The PhD degree certifies the ability for in-depth and independent scientific work.
It also says that one needs a written work (called dissertation) and an oral exam. For the dissertation there is
Die Dissertation muss die Befähigung der Verfasserin oder des Verfassers zu vertiefter und selbständiger wissenschaftlicher Arbeit nachweisen und einen Beitrag zum Fortschritt der Wissenschaft auf [insert some field] darstellen.
which is roughly
The dissertation has to certify the ability of the writer to do in-depth and independent scientific work, and to contribute to the advancement of science in [insert some field].
There are also some regulations for the oral exam but actually there is not a specific term what constitutes a passed or failed oral exam.
When I arrived to this question, there was (and probably still is) a highly upvoted comment:
"I fulfilled all of the requirements." — Austin Henley
I think that it's very easy for a new PhD or candidate to have serious doubts about the quality of their work, and to suffer a bit of the impostor syndrome. After all, they've spent numerous years seeing just how much knowledge is out there, and realizing that despite their new expertise, in the big scheme of things, it's actually a pretty small piece.
I've just completed my PhD, and one of the things that my advisor mentioned to me was very helpful, especially when I was feeling a bit of what I've described above. At my university, PhD students become candidates when they complete their candidacy, which includes their candidacy proposal, in which the student presents their research proposal to a committee (typically with members of their eventual examining committee) who must approve the proposal. My advisor reminded me that regardless of my own perspective on my research, the fact of the matter is that three or four years ago, a committee of experienced researchers, professors, etc., (i.e., my candidacy committee) reviewed my proposal and confirmed that the work it describes merits a PhD.
Based on that reminder, I framed by defense slides by beginning with a very quick review of the original candidacy, including a slide with a short problem statement. At the end of the defense, I pulled up another copy of that slide and addressed each point in the original problem statement, explaining how I'd addressed it. Then I followed with some "reveal text":
My research involved a fair amount of proof theory and formal logic, so this was especially appropriate, but the point remains: the work that I presented was that "which had to be demonstrated". The experienced committee said several years ago that the proposed work merits a PhD, and I completed that work.
The point here is that it's not really the candidate's place to determine what merits a PhD. They haven't, at that time, enough experience to make that determination. The university and committee does, and has already decided what merits a PhD, and it would be entirely appropriate to respond to the question "What merits a PhD?" with "you, as a committee member, explained that to me some number of years ago, and I've fulfilled those requirements."
The general requirement for getting a PhD degree is to produce novel research results (including of course writing them down in a dissertation and defending it in front of a committee). By this, you should show that you can work as an independent researcher.
one Professor was asking the defender why does he think, he deserves the degree.
If someone asks that during the defense, the answer should point out in which way the results are novel and a contribution to the current knowledge in the thesis' area of research.
For a Masters Degree, you are using existing knowledge and applying it to a new situation. For a PhD, you are creating new knowledge - you have discovered or invented something that was not known or existed before. If you can show that you have done this, you deserve a PhD.
Let's look at the abbreviation: PhD. Philosophiae Doctor which literally translates (my translation) as "Teacher of the beloved wisdom". (Doctor from doceo - to teach; philosophia from φιλος - dear, beloved and σοφια - wisdom or knowledge.
To be worthy of a PhD, you must therefore teach - which in the widest sense means add to the body of knowledge that came before. You are no longer learning - you traveled to the edge of the universe of knowledge, and boldly went where no-one had gone before. And - and this is a crucial element - you told stories of what you discovered when you came back.
The question is a good and fair one - and the answer should be obvious:
Through my research I have discovered [X,Y,Z] which I have taught the world through my publications and dissertation.
No need to blush - just state the facts.
A couple of years a senior and well-respected scientist that I know personally told me his perspective regarding what the title PhD means to him. I try to take that with me since then, especially at times of self-doubt.
He said the most important message that the title PhD conveys is that the holder has survived a significant period of time (3-5 years depending on where you live/work) in the academic world, battling with self-doubt, uncertainties in work, questionable guidance/project management, and many more challenges.
So, the way I see it; if you have survived until the end of your thesis defence AND fulfilled all criteria set by the university † (including original research), then you damn-well deserve the title and there's nothing anyone can fuss about. :)
Good luck with your work/defence.
† after all it's the university that grants the title, and thus its the institution's responsibility to make sure that the titles they bestow upon candidates is up to the international standard. It's their reputation on the line, as well.
This question is not a check if you are over self-confident or anything the like. Simply provide arguments why your PhD work matches the acceptance criteria that a valid for that institution. Your supervisor should know.
If criteria seem not obvious for some reason, emphasize the scientific novelty (some details you have investigated first ever) and any scientific recognition of the results (accepted papers, attended conferences). Negative results that just disprove the initial work hypothesis may be near equally significant.
