Donald Judd created simple box-like three-dimensional works that he called specific objects. These objects consist of several clearly defined parts that are arranged symmetrically. Judd was interested in the relationship between the whole object and the parts that make up the object. To avoid any ambiguity and not detract from their unitary quality, Judd employed clearly defined forms. He carefully chose materials for their reflective or transparent surfaces or for their dense textures. He chose colours for their visual clarity in defining angles and contours. In his work the coloured planes, volumes, and spaces interact in a clear and unified way. In 1983 Judd said: "Proportion is very important for us, both in our thinking and living, and visually translated, it is unity and harmony... and often peace and quiet." The objects do not refer to anything other than themselves. In the words of Roberta Smith: "Judd continues to make it clear that art is and always has been an object, and what makes objects art is not the way they mirror the world and mimic men, but the way they separate from the world and involve, through visual perception, access to the artist’s ideas and decisions."