The Disquotational Principle

I am preparing on writing a paper on Kripke and his essay, A Puzzle About Belief. In this Puzzle he raises (this is off the top of my head, so if I am wrong then forgive me) some problems about How we hold certain linguistically statements and how they associate with one's beliefs.  So, consider one of his puzzles

There is a man named Pierre, and Pierre learns that Skaowsky  is a famous polish pianist. He also learns that Skaowsky refers to a famous politician. Now, Pierre believes that no politician can produce good music, and thus, since Skaowsky is a politician he therefor cannot be a great pianist. 

This argument depends upon something called "the Disquotational Principle." This principle holds:

If S means P and a speaker understands and sincerely accepts (assents) to S, the the speaker believes P. 

DO ANY OF YOU THINK THAT THE PREVIOUS PRINCIPLE IS VALID? HOW WOULD ADJUST IT?