Rules in respect of that which happens. Principles according to which everything that can be presented to us as an object must conform to rules. Mathematics is made up of pure a priori principles that we may not ascribe to the pure understanding which is the faculty of concepts. Because they allow of intuitive certainty of evidential force and a priori application to appearances.
All appearances are extensive magnitudes.
Consciousness of the synthetic unity of the manifold is the concept of magnitude. A magnitude is extensive when the representation of the parts makes possible, and therefore necessarily precedes, the representation of the whole. This transcendental principle of mathematics makes pure mathematics applicable to objects of experience. Appearances are not pure intuitions like time and space . From empirical consciousness to pure consciousness a graduated transition is possible.