 Joseph Fourier, in a discussion with Monge, also took the concept of distance as fundamental, and began with three-dimensional space. He then employed equidistance to define successively the sphere, the plane (as the points equidistant from two given points) and the line (as the points equidistant from three given points). This did at least give him definitions of these previously troubling concepts (see Bonola 1912, 54).