Diriye Osman Author of Fairytales for Lost Children. Photograph: Boris Mitkov
When comes to reading and writing fiction, the theme can be confusing as some people mixing up the idea with the plot. To put it in a nutshell, the Theme is the writer's message and the central idea or ideas explored in the story whereas the plot describes the main events and sequence of a story. Many of us read books that explore specific themes sometimes without even realizing it. As a writer, that comes in handy because that's what attracts us to writing because the themes mean something on a personal and emotional level.
What is a Theme in Creative Writing?
One of the first questions we normally ask about a book or story is, "What’s the point of the story?" or "What’s it about?". Simply, the core idea, topic, or point of a story is its theme. A look in the dictionary can lead us to two definitions of the Theme:
The main subject that is being discussed or described in a piece of writing, a movie, etc.
A particular subject or issue that is discussed often or repeatedly
As you can see, the first definition is why many confuse the theme with the plot. So, let's take the second which focuses on the concept of a story in defining the theme. A theme can be expressed concretely in a very general way or as a broad subject and any creative piece can have more than one theme. Here's an example from Fight Club to understand the theme better and how to differentiate it from the plot:
Plot: A depressed man suffering from insomnia meets a strange soap salesman named Tyler Durden and soon finds himself living in his squalid house after his perfect apartment is destroyed. The two bored men form an underground club with strict rules and fight other men who are fed up with their mundane lives. Their perfect partnership frays when Marla, a fellow support group crasher, attracts Tyler's attention. (source)
The themes: Consumerism, Perfection, and Modernity, Masculinity in Modern Society, Death, Pain, and the “Real” (search for identity).
C.S. Lakin on her blog Live Write Thrive calls the theme "the heart of a story." I like the idea because the idea of an idea being the heart of a story makes you think what a theme should be like in order to be the heart of a story? For me, possibly, it's because a theme both shows a fundamental idea or moral that the character learns as a result of the plot, and meantime, it tries to teach something to the reader as well.
However, there might be confusion here about the primary theme and the moral of the story. I can say that these concepts are certainly related but they're not synonymous. "A book’s moral is a lesson the author wishes to impart upon their audience. (As such, morals are often key components to children’s books and young adult literature.) By contrast, a book’s theme is not so much its lesson as it is an idea the author hopes the audience will mine for deeper meaning." (Source)
As Michael Hauge, the author of Writing Screenplays That Sell, explains a theme "is the prescription for living that the writer wants to give the audience or the reader." He adds that the theme is connected to the main characters' journey and the lessons learned by him/her define the character arc and demonstrates their transformation for the readers and this way let the readers learn those lessons.
How Themes Works in Fiction (Motifs vs. Symbols)
As a writer, you may take different approaches to themes in your work. You might start with an idea, issue, or theme in mind, but you might find that there are other themes that grow, emerge, or develop from the main theme. Sometimes, it's a conscious process but mostly, you'll figure it while editing. Once you find them, that's when you can more easily decide what to cut from your story and what to focus on more. This is because every writer makes their writing about something, intentional or not. That something, the essence of the story, is its theme.