A painter strives to use elements and principles of art to unify the different parts of a painting. Unity is when all of the parts seem to make the picture strong and interesting.
In the Louisa Villea, the strong color red is used to draw attention to the subject, Louisa. It is then used randomly throughout the composition to support the subject and unify the artwork.
The repetition of shapes such as the roundness of Louisa's head, the roundness of the cherub's head, and the dome of the building work to unite subjects together.
The triangular shapes that repeat throughout the composition suggest a feeling of unity among the images in the painting....the wings on the birds, the wings of the cherub, Louisa's sleeves, the tops of the two buildings in the background.