John McCain and Honor

John McCain refuses to define honor in this interview.

There's a theme that recurs in your books and your speeches, both about putting country first but also about honor. I wonder if you could define honor for us?
Read it in my books.

I've read your books.
No, I'm not going to define it.

But honor in politics?
I defined it in five books. Read my books.

What's McCains problem? Couldn't he think of a definition? Was he worried that the concept of honor would be discussed in relation to his campaign? Is he just mentally deficient compared to the man he was 4 years ago?