[Nerwen]

Originally Posted by Inziladun

I think I've actually heard that theory before, though I seem to remember it being presented in a joking fashion.

However, the indications are that the Witch-king, as all the Nazgûl, was completely conquered by his ring, and an extension of Sauron's will.
In the Unfinished Tales chapter The Hunt For the Ring, we are told:

(empahsis added)

Also,



It seems clear there was no 'partial conquest' of the WK's will, allowing for inner debate. That was Gollum's problem.

I agree with you.