How to survive a thesis defence

Joe Wolfe
School of Physics
The University of New South Wales, Sydney

This document is an appendix to

How to write a thesis

• The thesis defence or viva is like an oral examination in some ways. It is different in many ways, however. The chief difference is that the candidate usually knows more about the syllabus than do the examiners.

• Consequently, some questions will be sincere questions: the asker asks because s/he doesn't know and expects that the candidate will be able to rectify this. Students often expect questions to be difficult and attacking, and answer them accordingly. Often the questions will be much simpler than you expect.

• In a curious relativistic effect, time expands in the mind of the student. A few seconds pause to reflect before answering seems eminently reasonable to the panel, but to the defender it seems like minutes of mute failure. Take your time.

• For the same reason, let them take their time. Let them finish, or even elaborate on, the question.

• The phrase "That's a good question" is useful. It flatters the asker and may get him/her onside, or less offside; it gives you time to think; it implies that you have understood the question and assessed it already and that you have probably thought about it before. If absolutely necessary, it can be followed by a bit more stalling "Now the answer to that is not obvious/straightforward..." which has some of the same advantages.

• Don't try to bluff your way out of a question. If someone has asked a simple question, and you answer with a torrent of jargon, or refer to some complicated equation, the other observers will probably conclude that you haven't answered a simple question with a simple answer. Now this may be both true and honourable: some simple questions cannot be answered simply. However, if you have to resort to complexity, you could begin by translating the question into your terms, defining them as you go, and, when you think you have answered, at least make an attempt to rephrase it in the language of the question.

• If the nightmare ever did come true, and some questioner found a question that put something in the work in doubt... mind you this is thankfully very rare.... then what? Well the first thing would be to concede that the question imposes a serious limitation on the applicability of the work "You have identified a serious limitation in this technique, and the results have to be interpreted in the light of that observation". The questioner is then more likely to back off and even help answer it, whereas a straight denial may encourage him/her to pursue more ardently. Then go through the argument yourself in detail - showing listeners how serious it is while giving yourself time to find flaws in it or to limit the damage that will ensue. In the worst caese, one would then think of what can be saved. But all this is hypothetical because this won't happen.

• What usually happens is that the examiners have read the work typically twice, and looked closely at some parts that interested them most. These are usually the good bits. The examiners have standards to uphold, but they are not out to fail you. (Administratively, it is a lot more complicated to fail you than to pass you!) In general, they feel good about the idea of a new, fresh researcher coming into their area. You are no immediate threat to them. They have to show that they have read it and they have to give you the opportunity to show that you understand it (you do, of course). And they usually have a genuine interest in the work. Some of them may feel it is necessary to maintain their image as senior scholars and founts of wisdom. Judicious use of the "Good question", "Yes, you're right of course", "Good idea.." and "Thanks for that" will allow that with a minimum of fuss and a maximum of time for champagne drinking.

• If one of the examiners is real nasty, your thesis defence is probably not the best place and time in which to do anything about it, except perhaps for allowing him/her to demonstrate his/her nastiness clearly and thus to establish the support of the rest of the panel. If you want a major dispute, save it up for when you are on even ground, unless you are very, very sure of yourself and think that you have nothing to lose.

• Be ready for a 'free kick'. It is relatively common that a panel will ask one (or more) questions that, whatever the actual wording may be, are essentially an invitation to you to tell them (briefly) what is important, new and good in your thesis. You ought not stumble at this stage, so you should rehearse this. You should be able to produce on demand (say) a one minute speech and a five minute speech, and be prepared to extend them if invited by further questions. Do not try to recite your abstract: written and spoken styles should be rather different. Rather, rehearse answers to the questions: "What is your thesis about, what are the major contributions and what have you done that merits a PhD?".

• Your viva is important. It is worth rehearsing it. Write down some questions (including nasty ones) and give them to a couple of trusted friends or allies. Have them ask you these questions, in as realistic a setting as you can manage, then answer, pretending that they are your jury, not your friends. Your friends can take notes about your style: they may have helpful advice. More importantly, however, you get to practise your answers and to rehearse giving them.

• Finally, a very important distinction. I wrote above: Take your time. This is not the same thing as 'Keep calm'. Most of us simply wouldn't be able to keep calm in this situation. Further, being excited or a bit nervous is actually helpful: with extra adrenaline, you can think more quickly. No, you don't want to be so nervous that you freeze up, but on the other hand, don't be scared because you are nervous: recognise that a bit of nervousness is a good thing. However, in spite of your nervousness, remember to take your time: don't rush.

• Now read the first two bullet points again. Good luck!

How to write a thesis

The University of New South Wales
School of Physics