Depth is the only defence
A written answer can be assembled from memorised phrases. A spoken answer, followed by "and why is that?", cannot. The examiner is not testing whether you can recite — they are probing for the edge of your understanding, and they are very good at finding it, because they have done this many times and you have not.
This makes the Feynman technique the single most relevant preparation there is: explain each concept out loud, in plain language, and notice where you stall. The place you stall is precisely where the examiner will land, and it is not a coincidence — you are both looking for the same thing.
Preparing properly
- Speak your answers, out loud. Silent revision does not prepare you to *speak*, and the gap between knowing and articulating is much larger than anyone expects.
- Get someone to ask 'why?' three times in a row. The third why is where the examiner lives. Most understanding survives one why and collapses at the third.
- Prepare the weaknesses of your own position. For a thesis defence especially: the examiner *will* find the limitation. It is enormously better to name it first, and to have thought about it.
- Practise saying 'I don't know'. Cleanly, without waffling, followed by what you would do to find out. Examiners respect this and are unmoved by improvisation, which they can hear coming.