Which principle of design is essential for creating a sense of wholeness?

Unity is essential for creating a sense of wholeness in a work of art because it refers to the harmonious relationship among the elements within a composition. When unity is achieved, all parts of the artwork come together to form a cohesive whole, making the work feel complete and balanced. This can be accomplished through repeated colors, shapes, textures, or patterns that connect different components of the artwork, leading to an inviting experience for the viewer.

In contrast, other principles like rhythm can evoke movement and lead the viewer's eye through the artwork but do not necessarily contribute directly to a sense of wholeness. Similarly, contrast emphasizes differences between elements to enhance visual interest, while variety introduces diversity and complexity to a composition but can potentially lead to fragmentation if not balanced with unity. Therefore, while these principles are important in their own right, they do not have the same central role in creating a cohesive visual experience as unity does.