I thought "an" meant "the"
Why does the 'e' have to appear twice just because you added the definite article?
I think I get it. If you didn't, you would get 'an an dochtuir e?' And it sounds stupid.
Why is, Is he the doctor , not acceptable
The An in this sentence is the interrogative copula, not the definite article.
An é an dochtúir é? - "is he the doctor?"