The PhD viva / thesis defense

By Dr. Rafiq Muhammad, MD, PhD · Updated June 2026

The viva (viva voce) or thesis defense is the last gate: an oral examination where you discuss and defend your thesis with examiners — usually one internal, one external. It feels like a trial, but the framing that calms most candidates is this: by the time you reach it, you are the world expert on your specific thesis. The examiners aren’t there to know more than you about it; they’re there to confirm you do.

What examiners are really testing

Behind every question are three things:

• Is it yours, and do you understand it? — that you can explain and own every choice.
• Is it an original contribution? — that the work adds something new to the field.
• Can you think critically about it? — including, crucially, its limitations.

They’re not trying to trip you up — they’re confirming you’re a competent, independent researcher who can defend your decisions.

Questions to expect

Most vivas open predictably: “Summarise your thesis in a few minutes,” “What’s your original contribution?” “Why did you choose this method over the alternatives?” “What are the limitations?” “What would you do differently?” “Where does this go next?” Prepare crisp, honest answers to these and you’ve covered most of the ground. Owning a weakness before they raise it reads as maturity, not failure.

A preparation plan

1. Know your thesis cold — re-read it closely; flag your contribution, methods, and limitations.
2. Prepare your summary — a tight statement of what you did and why it matters.
3. Anticipate & rehearse — list likely questions and answer them aloud.
4. Do a mock viva with peers or your supervisor; read your examiners’ relevant work.
5. List your own weaknesses with honest, prepared responses.

The outcomes — corrections are normal

The usual results: pass with no corrections (rare), minor corrections (most common), major corrections, revise-and-resubmit, a lower degree, or — rarely — a fail. Minor or major corrections are the norm, not a verdict on your worth. Handling them is the same disciplined, point-by-point work as responding to reviewers.