I think a lot of writers are automatically put off by the word symbolism. It's an idea a lot of people misunderstand, and to discuss the symbolism in a novel is--to some people--tantamount to announcing that the novel is difficult and likely very dull. "Oh, it's got metaphors," people groan. So I'm going to discuss symbols and symbolism and attempt to demystify this subject. I want to talk more about symbols in stories in the future, so this post is sort of an introduction to terms and general ideas.
A symbol is something that stands for something else. A stop sign is a symbol to drivers that they have to hit the brakes. A red cross is a symbol for a hospital. The color white means purity in some countries, mourning in others, death in yet others. In some cultures, lambs symbolize innocence. The '*' key on an adding machine means "multiplication." Et cetera. A symbol is one thing that stands in place of something else. We all use symbols, every day.
Symbols in literature fall into three types: simile, metaphor and allegory. Let's have a look at them.
A simile is a statement that compares one object to another, using the word "like." This thing is like this other thing is the basic formula.
His head is like a football is a simile. Similes are the most common form of symbolism. They are also arguably the least creative way of comparing things, because they are the most obvious and prone to cliche. His love for her was like a red rose is a cliche. Excuse me while I yawn.
This is the one that causes people confusion. It is essentially a simile without the word "like." The writer says that an object is another object, usually something not commonly associated with the first object:
His head is a football.
His love for her is a red, red rose.
Those are lame examples (especially the love/rose), but I've already used them so I'm sticking with them. The thing about metaphor as opposed to simile is that metaphors can be extended, stretched, to deepen the commentary about your subject:
His head was a football, hard and full of air. Real life was going to kick him into the goal on more than one occasion.
His love for her was a red, red rose, splendid for but a few days and then falling apart, petal by petal.
Metaphors can also represent things that aren't directly identified by the writer. This is where things get tricky. Suppose that you read a story in which every time a man told a certain woman that he was faithful to her, her candle would blow out. When it turns out that the man is NOT faithful to the woman, she is alone while he's off dallying elsewhere and her candle keeps going out. The flame going out becomes--through repetition in a single context--a symbol for his infidelity. This symbol is never apparent to the characters; it exists for the reader.
In my last book, the behavior of birds, singly or in flocks, mirrors the behavior of characters in the book. The condition of a garden represents the political situation (I stole that image from Shakespeare; thanks, old man!). In "The Lord of the Rings," the ring represents power which corrupts absolutely. The Ents personify nature lashing back at technology. The elven race, possibly, represents religion. Et cetera.
Allegory is a form of story where the characters act as stand-ins for other characters. Fables are frequently allegories, with talking animals standing in for types of people. "The Ant and the Grasshopper" is an allegory. "The Tortoise and the Hare" is an allegory. Hemingway's "The Old Man and the Sea" is a retelling of "The Myth of Sisyphus," so you could say it's an allegory of a metaphor. The play-within-the-play in "Hamlet" is an allegory.
There is a special type of allegory called a Roman a clef, which translates literally as "novel with a key." Romans a clef are allegories about real people, and the identities of those people are kept secret to avoid things like libel suits. These novels include a "key"--a clue, basically--to let clever readers "unlock" the secret and find out who the real people being discussed are. Political figures are sometimes written about via roman a clef, though nowadays it's becoming rare.
Why use symbols?
We use symbols for a variety of reasons. Similes are used primarily to describe things and people. Allegory is primarily used to teach a lesson (usually a moral one). Metaphor, the most slippery of symbols, has many uses. Metaphor can:
describe something in a poetic or lyrical way
be extended to add depth and dimension to the description
foreshadow events (in the love/roses example, if there are actual rose bushes in the story, they might catch a blight before the love story goes bad; or see the big storm in Act One of "Jane Eyre")
reinforce plot and character (the candle flame example, as well as all the references in "Hamlet" to poison and ears throughout the play)
bring out theme (in "The Overcoat," Gogol uses Akaky's overcoat to symbolize his place in society, and the treatment of his overcoat parallels the treatment Akaky receives).
All of this deepens the story, adding layers of meaning and understanding for the reader, even if the reader doesn't notice the symbolism (and maybe it's better if it's all subliminal anyway). Character, plot and theme can all be reinforced in subtle ways, so you aren't beating the reader over the head through repetition of dialog or events.
Symbolism is sort of a magic trick that allows you to tell the story in several languages at once. Don't be afraid of using it. If you make any use of symbolism (especially in a way I've neglected to mention here), tell us about it!