All of those examples before Quine were 'self-referential'. This means that they define an object in terms of itself, like the liar paradox starting with the words "this statement". Lots of people thought that you could ignore the liar paradox if you just decided to ignore all self-referential statements. Quine saw that you would also have to ignore "quotation", which is the process that happens when you put a phrase in quote marks. When you "say" a phrase, you are talking about its meaning; but when you "quote" a phrase, you are talking about that phrase, and not what it means.