Zhiyi's Interpenetrating Cosmos

Zhiyi, the sixth century founder of what became the Tiantai school in China, taught that every single moment of ordinary consciousness already contains the whole of reality within it, entire and without exception. The doctrine builds outward from ten realms of existence, running from the hell realms at the bottom up through the human and heavenly realms to buddhahood at the top, and holds that each of the ten in fact contains all ten of the others folded within itself, yielding one hundred realms in total rather than the original ten taken separately. Each of those hundred is then considered under ten characteristic aspects of suchness Zhiyi drew directly from the Lotus Sutra, and each of the resulting thousand realms is understood to operate across three distinct spheres of existence at once, the individual sentient being, the beings around it and the physical environment they all share, producing the three thousand realms said to be present, complete and entire, in any single instant of ordinary thought. The force of the claim is that buddhahood is not a distant destination reached only after eliminating the other nine realms from oneself one by one, since if every realm already interpenetrates every other realm, the realm of buddhahood is already fully available within this present, ordinary moment of mind.