Correlative Quotes
The concept-systems of antithesis are concepts that are indeed thoroughly determined by negative predicates but are not positively representable.
Just because a precise and complete representation of these concept-systems is impossible, they are inaccessible to direct investigation and elaboration by our reflection. They may, however, be regarded as lying at the limit of the representable, i. e., we can form a concept-system lying within the representable, which passes over into the given system by simple change of magnitude ratio. By abstracting from the ratios of the quantities, the concept-system remains unchanged in case of transition to the limit. At the limit itself, however, some of the correlative concepts of the system lose their susceptibility of being represented, and those, indeed, that mediate the relation between other concepts.
Bernhard Riemann
Within the ranks of the people, democracy is correlative with centralism and freedom with discipline. They are the two opposites of a single entity, contradictory as well as united, and we should not one-sidedly emphasize one to the denial of the other. Within the ranks of the people, we cannot do without freedom, nor can we do without discipline; we cannot do without democracy, nor can we do without centralism. This unity of democracy and centralism, of freedom and discipline, constitutes our democratic centralism. Under this system, the people enjoy extensive democracy and freedom, but at the same time they have to keep within the bounds of socialist discipline.
Mao Zedong