 With the intuition that distance is the primitive concept comes a greater appreciation of motion, or at least the results of being able to move objects around without altering them. One can imagine transporting a rigid body around, say a cube with sides of unit length, and using one of its sides to mark out lengths. We shall see later that the possibilities inherent in this process occasioned a chicken-and-egg debate between Bertrand Russell and Henri Poincaré at the end of the 19th century.