  Riemann searched for the most general type of an \(n\)-dimensional manifold. On this manifold, Euclidean geometry turns out to be a  special case resulting from a certain form of the metric. Weyl takes  this general structure, the manifold structure, which has certain  continuity and order properties, as basic, but leaves the  determination of the other geometrical structures, such as the  projective, conformal, affine and metric structures, open. The  metrical axioms are no longer dictated, as they were for Kant, by  pure intuition. According to Weyl (1949a, 87), for Riemann the metric is not, as it was for Kant, “part of the static homogeneous  form of phenomena, but of their ever changing material  content”. Weyl (1931a, 338) says: 