Nichiren understood the revelation of Buddha’s inconceivable “lifespan” as the very heart of the sūtra. The sūtra text makes clear that, even after realizing buddhahood, Śākyamuni has remained in the world, and will continue to do so, for countless eons, “teaching the dharma and inspiring sentient beings.” For Nichiren, this signaled a seismic shift in the entire concept of buddhahood as a realm apart from the nine realms of ordinary experience. Conventional understanding holds that the cause of buddhahood and its effect, that is, practice and attainment, are separated in time. To become a buddha, one must carry out the practices of the bodhisattva for three immeasurable eons, a staggering length of time spanning countless lifetimes. The “trace teaching” or shakumon portion of the Lotus Sūtra, even while extending the promise of buddhahood to all beings, still preserves this perspective on realizing buddhahood as a linear process in which one moves from practice (nine realms) toward attainment (buddhahood). We see this in Śākyamuni Buddha’s predictions in the sūtra’s early chapters that his individual śrāvaka disciples such as Sāriputra, Mahākāśyapa, and others will become buddhas in the remote future, after many eons of bodhisattva practice. From this perspective, buddhahood remains a distant goal, abstracted from one’s present experience.

But with the origin teaching, Nichiren wrote, the cause and effect of the pre-Lotus Sūtra teachings and of the trace teaching are “demolished” and “original cause and original effect” are revealed: “The nine realms are inherent in the beginningless buddha realm, and the buddha realm inheres in the beginningless nine realms. This represents the true mutual inclusion of the ten realms … and three thousand realms in a single thoughtmoment.” That is, he saw the origin teaching as overturning linear views of practice and attainment, in which one first makes efforts and then realizes buddhahood as a later result, and revealing that cause (the nine realms) and effect (the buddha realm) are present simultaneously; buddhahood is manifested in the very act of practice.