Famed theorist and statesman Edmund Burke once said, "Poetry is the art of substantiating shadows, and of lending existence to nothing." Working in different eras and mediums, artists have attempted to capture this most elusive of visual phenomena: the shadow. These artworks feature images of shadows, either as subject matter or formal elements. Especially in photography, patterned shadows are used to create a visual effect. (For the use of dramatic shading to create the illusion of volumes in space, see Chiaroscuro.)