What makes a writer?

Following my earlier post, Mark asks at a coffee shop: If not education then what makes a writer?

I am not arguing that formal education is useless for one who wants to write, but I find that it is more than the ability to learn that aids one in his/her writing. If I were to pick the single most important trait a prospective writer should posses, it would have to be curiosity.

Writing, much as the quality of knowledge one acquires, is dependent on curiosity, the ability to ask questions. A writer is like a child - always asking. Not far behind is the ability to ask just the right questions. Notice how those who seldom ask are usually those whose knowledge is founded on very shaky ground - these are often people who think they know the answers.

To me - knowing means doubting. Doubting means asking. Writing is posing a question, which explains why I can't stand works of writers who think they have all the answers.