[T]he two teachings – the Tripiṭaka teaching and the Common teaching – do not espouse the idea that ordinary people in the Six Realms originally have the Buddha-nature. They preach instead that one can be a śrāvaka, pratyekabuddha, bodhisattva, or Buddha only by practicing the way leading to each of them.

Ichidai Shōgyō Tai-I, Outline of All the Holy Teachings of the Buddha, Writings of Nichiren Shōnin, Doctrine 3, Page 74