Were it not for the presence of the “Life Span” chapter among all the teachings of Shakyamuni, they would be like the heavens without the sun and moon, a kingdom without a king, the mountains and seas without treasures, or a person without a soul. This being so, without the “Life Span” p.184chapter, all the sutras would be meaningless. Grass without roots will die in no time, and a river without a source will not flow far. A child without parents is looked down upon. Nam-myoho-renge-kyo, the heart of the “Life Span” chapter, is the mother of all Buddhas throughout the ten directions and the three existences.
---> http://www.nichirenlibrary.org/en/wnd-1/Content/18