Day has used 17th century models of the five regular polyhedra (Plato's stages of awareness outlined in his famous dialogue the Republic) known as the Platonic Solids as his models. Cutting and painting the illusionistic figures from flat sheets of fibreboard and mounting them on adjustable brackets so that they can cast deceptive shadows. The Platonic Solids, known since Pythagoras, have an illustrious history. Considered fundamental by the ancient Greeks, they were rediscovered during the Renaissance and illustrated by Leonardo for a work on perspective. Johannes Kepler (1571-1630) thought that he had discovered the underlying organization of the universe within the relationships between the five shapes. In the last century Werner Heisenberg (1901-1976) said that the shapes played a crucial role in his own development of the ideas of quantum theory.