But where the limits of our possible knowledge are very narrow, negative instructions guard us from error. Distinguished from culture which is intended to give a certain kind of skill. Discipline will contribute in a negative fashion to the development of a talent, culture in a positive. When reason is being considered in its transcendental employment it stands greatly in need of a discipline to restrain its tendency towards extension beyond the narrow limits of possible experience. Philosophical knowledge is the knowledge gained by reason from concepts.
Mathematical knowledge is the knowledge gained by reason from the construction of concepts.
To construct a concept means to exhibit a priori the intuition which corresponds to the concept. For the construction of a concept we need a non-empirical intuition . This non-empirical intuition must be a single object. It must also express, in its representation, universal validity for all possible intuitions which fall under the concept. This is the essential difference between these two kinds of knowledge and not the difference of their material or objects.