Non-Buddhist religions in India claimed that this world was eternal, joyful, free and pure. On the contrary, the Buddha insisted that this world was impermanent, painful, empty and egoless in order to destroy their superficial views. The Two Vehicles (two kinds of Buddhist known as śrāvaka and pratyekabuddha) were stuck to the principle of emptiness preached by the Buddha and could not grasp the idea of eternity in Mahāyāna Buddhism. The Buddha, therefore, reproached them saying that even the five rebellious sins and evil passions could be a cause of enlightenment, but their inflexible belief in emptiness will never lead them to Buddhahood.

Jisshō-shō, A Treatise on the Ten Chapters of the Great Concentration and Insight, Writings of Nichiren Shōnin, Doctrine 2, Page 5