"The mutual possession of the Ten Worlds is as difficult to believe as fire existing in a stone or flowers within a tree. Yet under the right conditions such phenomena actually occur and are believable. To believe that Buddhahood exists within the human world is the most difficult thing of all—as difficult as believing that fire exists in water or water in fire. Nevertheless, the dragon is said to produce fire from water and water from fire, and although people do not understand why, they believe it when they see it occur. Since you now believe that the human world contains the other eight worlds, why are you still unable to include the world of Buddhahood? "
From Gosho "The Object of Devotion for Observing the Mind" (The Writings of Nichiren Daishonin Volume I, page 359)
From Gosho "The Object of Devotion for Observing the Mind" (The Writings of Nichiren Daishonin Volume I, page 359)