Focusing on one symbol, write an essay analyzing how that symbol functions in Frankenstein and what it reveals about the characters or themes of the work as a whole.

There are numerous symbols in Mary Shelley's Romantic novel Frankenstein. Many of the symbols are representative of either a specific character or theme presented in the novel.
First, a symbol in a text attaches meaning deeper than the face value of the image. Symbols tend to allow figurative "threads" to wind throughout a text, bringing more meaning to the image, character, or symbol than initially thought.
One important symbol in the novel is light. Typically in literature, light functions as a symbol of knowledge. This specific symbol is important, given that many of the characters in the text are on a quest for knowledge. Light for Victor represents his unraveling of scientific mystery surrounding life and death. Over the course of the novel, as Victor sheds more and more light upon life and death, the mystery surrounding life and death diminishes. Unfortunately for Victor, this knowledge leads to his downfall and destruction.
For the Creature, light works a little differently. First, upon waking, the Creature feels intense pain. He closes his eyes, and the pain subsides. It seems that, for the Creature, light (or knowledge) is something that he must avoid. After realizing that light from the sun hurts his eyes, he travels at night. Lured by the small light of a fire, the Creature finds that light physically hurts him again. Yet, this time, he learns how to use the light of the fire to roast nuts (making them taste better). Later, the Creature is enlightened further when he looks into a pool of water. He is horrified by his reflection, something he has never seen. This new knowledge saddens the Creature. For the Creature, avoiding light (knowledge) may have been better.
Robert Walton, the narrator of the novel and Victor's last friend, also illustrates the symbolism associated with light. He is on a course to discover the "seat of magnetism." He wishes to focus light (knowledge) on new paths to the North. During his voyage, he is willing to give everything up to find success. In the end, Victor intervenes, telling Walton of the error of his own ways, in order to veer Walton off the same destructive path.
In regards to how the symbolism of light affects or illuminates the theme of the novel, one of the themes is the search for forbidden knowledge. Figuratively, forbidden knowledge is the knowledge that man should not interfere with. It is the knowledge kept in a figurative darkness, only to be illuminated when someone discovers the light needed to shine upon it. Throughout the novel, as forbidden knowledge is brought out of figurative darkness, each of the characters involved puts himself on a path to destruction.
Therefore, the novel and its author are offering readers a warning against interfering with nature and the things which are off-limits to mankind. By keeping mankind in darkness, nature is able to keep ultimate control of the world.