Imagine your thesis is an iceberg.
You can see it floating in a sea of knowledge. Big and beautiful, possibly dangerous! A hazard for other ideas, crashing and crushing, but approached carefully you can study it. Someone can think about how it relates to other icebergs/theses, what it means. They can dream up questions about it. Depending on who that someone is, depending on their experience – their own icebergs – those questions could be tricky…
But there’s more than what’s on the surface.
If an examiner or anyone else reads your thesis they see the surface iceberg. Your research and experience are underwater: a massive bulk of knowledge, skill, time, patience, talent, persistence. Quietly hidden, but there all the same.
Your examiners can ask about what they see on the surface, make guesses perhaps at what else is in the watery shadows.
You appreciate it all though; the surface iceberg-thesis and the experience-knowledge-skill-time-patience-talent-persistence-ice-mountain of research beneath the surface. It’s all there for you when you need it, hiding in the depths.