Our eyes are trained to look for Unity as we try to make sense of the world around us.
Artists and Designers must create a unified image. Otherwise the viewer is likely to pay little attention to a composition. Proximity Repetition Continuation
are some ways to achieve UNITY.
Most artists use a combination of these factors to achieve Unity. Alicia MacCarthy's above and Piet Mondrian's paintings below exhibit Unity with Repetition and Continuation.
Mondrian's paintings also illustrate very clearly the concept of Continuation and Repetition by employing a grid design.
Andy Warhol often used Repetition and Proximity to create a sense of unity in his paintings and silk screens.
William Wegman's triptych illustrates Repetion, showing how the slightest shift in perception can have a surprisingly strong impact.
Griorgio Morandi's quiet studies of vessels express Unity through Proximity and Repetition with variety. The way the vessels are arranged close together make for a cohesive composition.The restrained value of the paintings, how the shades of the colors are all very close on a gradation scale also lends a sense of subdued Unity.
Tara Donavan uses Repetition to achieve Unity when she makes sculpture with everyday materials. By using thousands of these cups she creates a form that is perceived as a whole, a sort of landscape...not a lot of separate cups.
There is overlap among the noted ways to achieve unity. Sometimes it is hard to distinguish between them. This is not an exact science. It is Art. Everyone can have a different view. Just be sure to look carefully before you make up your mind and try to figure out what makes the composition work.