One of the ways that artists create unity in works of art is through symbolism. By using symbols that represent other ideas, those ideas can be present in the works of art to help the participant better understand the content of the work. In the color lecture the symbolism of color is explored: green - fertility, red - anger or love, blue - truth or sadness, etcetera. Symbolism can also exist in ideas associated with objects presented in the work. This work is an example of Vanitas. This refers to works that remind the participant of the impermanence of life. It typically features materialistic objects and a skull. The skull, located near the top of the work, is a symbol representing death. It is surrounded by the accumulated possesions that cannot be taken into the afterlife.
Iconography is a more specific type of symbolism.