Reason has a natural tendency to transgress its limits and transcendental ideas are as natural to it as the categories are to the understanding. We are entitled to suppose that transcendental ideas have their own good, proper and therefore immanent use. Just as the understanding unifies the manifold in the object by means of concepts, so reason unifies the manifold of concepts by means of ideas. Reason does not create concepts, but only orders them.
Transcendental ideas have regulative employment which is necessary to understanding.
They direct the understanding towards a certain goal upon which the routes marked out by all its rules converge. They serve to give to concepts the greatest possible unity combined with the greatest possible extension. Reason prescribes the systematization of the knowledge obtained by the understanding. It seeks to exhibit the connection of its parts in conformity with a single principle. It presupposes the idea of the form of a whole knowledge which is prior to the determinate knowledge of the parts and contains the conditions that determine a priori for every part its position and relation to other parts.