"The danger is this: When your Premise is an idea you feel you must prove to the world, and you design your story as an undeniable certification of that idea, you set yourself on the road to didacticism. In your zeal to persuade, you will stifle the voice of the other side.
Misusing and abusing art to preach, your screenplay will become a thesis film, a thinly disguised sermon as you strive in a single stroke to convert the world. Didacticism results from the naive enthusiasm that fiction can be used like a scalpel to cut out the cancers of society.
As a story develops, you must willingly entertain opposite, even repugnant ideas... [The finest writers] see the positive, the negative, and all shades of irony, seeking the truth of these views honestly and convincingly. [...] Ultimately, they express what they deeply believe, but not until they have allowed themselves to weigh each living issue and experience all its possibilities."