To make it simple, your screenplay theme is the perspective your Main Character has after they’ve finished their journey.
Let’s look at a few examples:
In Kramer vs. Kramer (1979), Ted Kramer (Dustin Hoffman) goes from not wanting to be a single father to learning his greatest accomplishment is being a great dad. The theme? Divorced fathers can be excellent custodial parents. Remember in the 70s, this was a thing as courts always sided with the mothers.
In Murder on the Orient Express (2017), Hercule Poirot (Kenneth Branagh) is a strictly by-the-book right vs. wrong kind of man who has to compromise these fundamental principles to allow people who’ve done wrong to go free. The theme being there are no absolutes when it comes to murder. Sometimes circumstances create killers from victims and vice versa.
One more. Black Panther (2018). A film that has so many important social and cultural themes it is hard to narrow it to just one. But the theme of self-identity reflects an African-American culture at war with itself and struggles to achieve in a divided America. This is from a great study guide by Grade Saver:
Writing about Black Panther for The New Yorker, Jelani Cobb describes African-American identity as “two feuding ancestries conjoined by a hyphen.” He posits that there is a fundamental tension in the very notion of being African-American because to be black on some level means being not totally accepted as an American by much of society. And yet they cannot reject this identity because it has been forced upon them by history and circumstance.
Ryan Coogler was all over that shit in the movie.
So how do you thread your theme?
Watch movies. Compile a list of where the Main Character is at the end. What must they sacrifice? Is it their principles? Their former way of life? Their child?
Know where your Main Character is at the end of your screenplay emotionally. After taking a tumultuous ride for ninety pages, how are they doing? Once you take their pulse you can see their attitude about what’s happened over the course of the story.
In Big (1988), 12-year-old Josh Baskin (David Moscow) becomes 30-year-old Josh (Tom Hanks) after wishing he was “big.” It takes his journey through an adulthood he’s certainly not ready for to realize he’d rather be 12. He has to sacrifice the grown up life including a mature relationship to return to his family and friends. His attitude is relief and gratitude about not being big. Lesson learned. The theme of appreciating where you are in your life cycle is also reflected in his adult girlfriend, Susan (Elizabeth Perkins) who at the end when Josh asks her to become 12 so they can stay together, she refuses stating she was 12 once and that was enough.
Even action movies follow these thematic examples. Armageddon (1998) may be about the imminent destruction of the plant, but through Bruce Willis’s sacrifice it’s really about making sure his daughter gets married to Ben Affleck. His external goal to do his job dovetails with the inner goal to see Liv Tyler happy. The rest of the story serves that goal. Even if it costs him his life.
In addition to knowing your Main Character’s sacrifice and attitude toward it at the end, another key to finding your screenplay theme is to understand your character’s main goal. What do they want at the beginning and how does that goal change in the middle? If you’ve done your job correctly, by the last act, the original goal will have changed to something the character either rejected or did not know they wanted.
Romantic comedies are really great at this. Baby Boom (1987) is not about neurotic go-getter JC Wiatt (Diane Keaton) leaving corporate America to raise a baby she was given responsibility for in a relative’s will. It’s about finding true love with a compassionate, laid back veterinarian Jeff Cooper (Sam Shepard).
One of my favorite rom coms is French Kiss (1995). Kate (Meg Ryan) chases her fiance (Timothy Hutton) who’s fallen in love with someone else and broken the engagement. She tracks him down in France where with the help of a French louse, (Kevin Kline) she is able to lure him back only to realize she doesn’t want a sap so easily turned. She wants real love with a strong man who loves her. Oh, there’s Kevin Kline who fits the bill. Convenient.
That’s a primer. Learning your screenplay’s theme is a necessary evil when creating your outline. If you don’t have an outline, beat sheet, treatment, something, shame on you. You have to know where you’re going before you get behind the wheel.
If you establish the main character’s goal, how that goal changes, what they have to sacrifice to achieve it and the attitude at the end of the journey, you will not only have a solid theme to sell to producers, but a satisfying screenplay for readers.