What is Symbolism?
A symbol in poetry is something that is used not only literally but also as a way to represent something else. So, for example, a poem might be about an oak tree and the cycle of life of a tree. The oak itself is what the poem is about, but it might also be meant as a symbol for human life. A symbol differentiates itself from a metaphor in that while a metaphor compares two unlike things, such as "my life is an oak tree," a symbol simply gives the object and allows the reader to make the comparison.
What is Allegory?
Allegory refers to a complex collection of symbols that work together in one coherent text; in an allegorical poem, the entire poem works as a set of symbols. So, to add to the above oak metaphor, an allegorical poem might include not only an oak, but a person who comes to tend the oak, which might represent friends and family, and a person who comes to cut the oak down, who might represent death.
How to Identify Both
Whenever you find a poem that repeatedly uses a particular object or description, try to shift to symbolic thinking to see whether this object or description is serving a double purpose. Often, poems that use symbols or metaphor will describe an object or other symbols using descriptors that can help the reader know how the object is working symbolically. For example, in the poem "The Fish" by Elizabeth Bishop, word choice used to describe the fish provide the reader with clues about what the fish symbolizes to the narrator; for example, the fish is described as "wise," but also "dangerous." When analyzing for symbol or allegory, ask what the language used might tell us about the symbol and ask if the scenario described in the poem could work as a larger allegory.
What Do They Add?
Symbolism and allegory add a depth of meaning and interpretation to a poem. While, on the surface, a poem might simply be about appreciating nature or celebrating a particular person or idea, reading a poem symbolically might reveal several layers of meaning beyond the obvious surface levels.
Example of a Symbolic Poem
One of the most famous examples of symbols comes from the poem "The Fish." The poem centers around a narrator catching a fish, and while on the surface it might seem merely like a description of an event, the poem's word choices reveal that "The Fish" is about something more than simply a fishing trip. Bishop describes the fish as "terrible," having a "sullen face," and previous hooks in his lip that looked like "a beard of wisdom." The fish becomes a symbol for many things: life force, wisdom and the beauty of nature. When the narrator finally throws the fish back in the water, it becomes clear that the poem is not only about this individual experience but also experiences with the wildness of nature and beauty in general.
Example of an Allegorical Poem
One of the most famous allegorical poems in English is John Bunyan's "Pilgrim's Progress." This poem is the tale of "Christian," who represents any individual Christian person (specifically a Puritan individual, because this is the religious position that Bunyan is writing from) and his journey to the "Celestial City," which represents heaven. The entirety of the poem is devoted to showing the various stumbling blocks and challenges that Christian has to overcome to make it to his destination. This poem is simultaneously about the actual story, of a man named Christian, but it also a wider allegory about the Christian path to salvation.