Themes or motifs are often presented through symbols — that is, images used in such a way as to suggest a meaning beyond the physical facts of the images themselves.
Two quite effective symbols in Bleak House are the fog and “the Roman” who points down from Mr. Tulkinghorn’s ceiling and symbolizes the theme of retribution, of evil ultimately bringing ruin upon itself.
Skillfully handled, symbolism adds both impact and unity to a literary work — or, for that matter, to any piece of writing. It has the impact (also called “power”) of the concrete, and it helps unify because it repeats in a different form the motifs that are being presented through plot and character portrayal. Symbolism is commonly called a “device” or “technique,” but these terms are somewhat misleading because they imply conscious manipulation by the author and also imply that effective symbolism is external and might be learned by anyone in a classroom or from an instruction manual on how to write. At its best, symbolism comes straight out of the individual writer’s unconscious artistry: It is instinctive and individual and often a mark of genius.
Symbols are often used to foreshadow later events in a story.
In turn, the “technique” of foreshadowing lends unity to the story because it prepares us by dealing with things that will be developed later on. The Bleak House fog is a complex symbol that foreshadows several motifs of importance. Richard Carstone, for example, gradually becomes “lost,” unable to “see,” in the mental and spiritual fog generated by the High Court of Chancery.