Proof of the existence of Buddhahood

"The Lotus Sutra, explaining the world of Humanity, says that '[the Buddhas appear in this world] to open the door of Buddha-wisdom to all beings.' The Nirvana Sutra states: 'Those who study the Mahayana teachings, though they have the eyes of ordinary mortals, are said to have 'the eyes of a Buddha.' That common mortals born in the Latter Day of the Law can believe in the Lotus Sutra is due to the fact that the world of Buddhahood is present in the world of Humanity.'" -- The True Object of Worship