A question asked of Merlin by King Arthur in the (GREAT) Movie- Excalibur (1981)
I’ve been involved in a discussion on this topic *here* on the Armour Archive – and thought it deserved a spot in my SCA Ramblings section…
I used to think it was Duty but the more I grow the more I think of it, the more I believe Merlin has the right of it, remember the question Arthur asks isn’t which one can a knight be without, but which is the greatest.
Merlin answers they blend like the metals you use to make a good sword…its when Arthur pushes him for a straight answer he says “Truth”. I say the core that holds them together is truth…
The ability to be honest with ones self and when to apply the strength of the other virtues and when to hold one back in lieu of another…they are most linked with each other but all linked by truth.
The difference between Confidence and Arrogance is the recognition of the truth of ones limitations and accepting of ones limitations and faults. which is part of humility.
If you are humble you must be honest with yourself and know when to stand up for yourself or others, which is part of courage.
and so on – they do all blend together like the fine metals and craftsmanship of a sword, but without the temper of truth…the sword is more brittle.
but that is me…
by the way you can find the exact conversation in the movie here at 5minutes and 10 seconds…
Excalibur YouTube

Very well put Sir Ulrich. I believe that truth is the greatest of qualities in all people, but especially for those, such as the chivalry, who are held to higher standard than most people hold themselves to.