Nichiren's teachings developed over the course of his career and their evolution can be seen through the study of his writings as well as in the annotations he made in his personal copy of the Lotus Sutra, the so-called "Chū-hokekyō". Some scholars set a clear demarcation in his teachings at the time he arrived at Sado Island whereas others see a threefold division of thought: up to and through the Izu exile, from his return to Kamakura through the Sado Island exile, and during his years at Minobu. According to Anesaki, Nichiren, upon his arrival at Minobu, quickly turned his attention to consolidating his teachings toward their perpetuation. The scope of his thinking was outlined in an essay "Hokke Shuyō-shō" [法華取要抄, "Choosing the Heart of the Lotus Sutra"], considered by Nikkō Shōnin as one of Nichiren's ten major writings. Anesaki also claims that later during his Minobu years, in lectures he is said to have transmitted to his disciples, Nichiren summarized the key ideas of his teachings in one paragraph: Buddhahood is eternal, all people can and should manifest it in their lives; Nichiren is the personage in the Lotus Sutra whose mission it is to enable people to realize their enlightenment; his followers who share his vow are the Bodhisattvas of the Earth. This requires a spiritual and moral unity among followers based on their inherent Buddhahood; Nichiren established the seeds of this community and his followers to come must extend it globally. Thus the enlightened individual, country, and world are different expressions of the ideal of the Buddha land; and the enlightened heart of the individual plays out its role with the world and cosmos as its stage. This is Nichiren's vision of "Kosen-rufu", a time when the teachings of the Lotus Sutra would be widely spread throughout the world. Nichiren set a precedent for Buddhist social activism centuries before its emergence in other Buddhist schools. The uniqueness of his teachings was his attempt to move Buddhism from the theoretical to the actualizable. He held adamantly that his teachings would permit a nation to right itself and ultimately lead to world peace. Some of his religious thinking was derived from the Tendai understanding of the Lotus Sutra, syncretic beliefs that were deeply rooted in the culture of his times, and new perspectives that were products of Kamakura Buddhism.