  Physical dynamical quantities in spacetime, such as the geometrical  structural fields on the four-dimensional spacetime continuum, are  describable as functions of a variable point which ranges over the  four-dimensional number space \(\mathbb{R}^{4}\). Instead of  thinking of the spacetime points as real substantival entities, and  any talk of fields as just a convenient way of describing geometrical relations between points, one thinks of the geometrical fields such  as the projective, conformal causal, affine and metric fields, as  real physical entities with dynamical properties, such as energy,  momentum and angular momentum, and the field points as mere  mathematical abstractions. Spacetime is not a medium in the sense of  the old ether concept. No ether in that sense exists here. Just as  the electromagnetic fields are not states of a medium but constitute  independent realities which are not reducible to anything else, so,  according to Weyl, the geometrical fields are independent irreducible physical   fields.[62] 