Polarity, or action and reaction, we meet in every part of nature. - Ralph Waldo Emerson
In screenwriting, polarity is bliss. Why? Because polarity is mutual opposition, and when opposite elements are forced to interact, sparks fly. Conflict! It's the elixir of the script, the adhesive that keeps us there. If there's no conflict, there's no audience; therefore, conflict is the moviegoer's aphrodisiac.
Good and evil: Star Wars. Black and white: The Defiant Ones. Men and women: When Harry Met Sally. These films are based on polarity, with characters so diametrically different that conflict is inevitable.
Sometimes the polarity is a cut and dry opposition between protagonist and antagonist: Luke Skywalker vs. Darth Vader. But often it occurs within an unlikely team. A classic example is The Defiant Ones (1958): Two escaped convicts chained together, one white (Tony Curtis) and the other black (Sidney Poitier), must overcome their prejudices and work together to elude capture.
We need polarity in screenwriting, not only because it creates great conflict, but it also allows for the opportunity for a character to learn and even change his or her position on race, sex, or ideology. Change is strength, and if we watch a character start seeing the world differently - with an open mind - then there's hope for the audience as well.
Polarity in Action:
The Odd Couple (1968) Felix Ungar (Jack Lemmon) and Oscar Madison (Walter Matthau) are two divorced friends sharing an apartment, but their lifestyles and ideas of housekeeping mix like oil and water. Felix is a weak, paranoid, little man, fueled with anxiety. He’s a neat freak, a master in the kitchen, incredibly organized, but a nervous wreck. His counterpart, Oscar, is a confident, but irresponsible slob, whose idea of housecleaning is sour milk, moldy sandwiches and spaghetti on the wall. The opening poker scene alone is enough to make you fall off the chair laughing. In this film, the conflict comes out through humor and arguments alike.
Lethal Weapon (1987) Sgt. Roger Murtaugh (Danny Glover) is a veteran cop who is assigned to work with Sgt. Martin Riggs (Mel Gibson), a young homicidal cop, to stop a gang of drug smugglers. Do they have anything in common? Only the fact that they are both lethal weapons. Riggs is white, around 30, a widower and single, self-destructive, suicidal, careless, yet charismatic with a good sense of humor. Murtaugh, on the other hand, is black, turning 50, happily married with kids, responsible, pragmatic, but a bit stiff and up-tight. Without even writing one word in the script, just by creating characters that are opposites in almost every way, the conflict arrives on it’s own. The writer doesn’t have to look for it.
Shanghai Noon (2000) In this action-comedy, an unlikely duo - Chinese Imperial Guardsman and bumbling Wild West train robber - work together to rescue a princess and take on a Chinese slave traitor. Again, the characters are what make the story work. Roy O’Bannon (Owen Wilson) and Chon Wang (Jackie Chan) are on polar ends of the character spectrum. Roy is a failed American outlaw on the Western frontier, who can’t fight, can’t shoot, can talk his way out of a jam, and originally joins the quest only because he’s in it for the money. Wang, in contrast, is a skilled member of the Chinese Imperial Guard, with expert fists of fury, a man of few possessions and even fewer words, who will stop at nothing until he completes his royal mission of honor, which to him is worth more than all the gold pieces in the China.