This theorem marks an event in the history of geometry. From the beginning geometry was concerned with measures: lengths of lines, areas of plane figures, volumes of bodies. Here we have for the first time a theorem which is established by the ordinary theory of measures but is itself free of all elements of measurement; it states the existence of a figure which is determined through the incidence of lines and points only. It is the first ‘configuration’ of projective geometry, and it was shown more than 1500 years later that this configuration alone is sufficient to build up projective geometry in the plane.