In this text, I present a Buddhist heterodoxy of my own making based on commentary on the Nirvana Sutra, which is not my own. With it, I add what little I know of Nembutsu practice which I call "non-practice" and of Buddhism, which I consider a "non-religion". Both terms - non-practice and non-religion - are explained, and a vow not to make this heterodoxy a Buddhist sect teaching it is made.
Buddha Nature is present always, in all times and in all being.
Yet it is hidden (occulted) from view by tenacious negative mental afflections (kleshas) within each of us. The most notable of afflictions are greed, hatred, delusion and pride.
Once these mental states have been brought to rest, Buddha Nature shines forth unimpeded. Then the Buddha sphere (a state of mind called visaya) can be consciously "entered into", and deathless Nirvana attained. Thus, Buddha Nature is that Buddha sphere and another name for it is visaya.
Mahanirvana, contrary to being death and the end of life, is Eternal, Blissful, the Self and Pure. However, this state (sphere) of ultimate awareness and Knowing, is accessible only to full awakened Buddhas.
Not even the the highest of Bodhisattvas are able to clearly see the Buddha sphere. Indeed, they fail to see with clear mind that the immutable unfabricated Buddha Nature dwells indestructibly within all beings.
Because of Buddha Nature permeating all forms of life, absolutely all beings without exception, even the lowest of all, will eventually attain Liberation (Nirvana) and become Buddhas.
Thus, for a Nembutsu practitioner such as I, through the merit of Amida Buddha's name, this revelation inspires me to continue with Nembutsu whilst considering it a non-practice and Buddhism itself as non-religion to be consistent with the Buddhist ideal of non-self.
For Nembutsu practice is a non-practice in that, due to physical limitations, a practitioner cannot practice it forever yet a countless number of practitioners have uttered the Nembutsu since its practice countless æons ago.
Furthermore, Buddhism itself is a non-religion in that it arose because of dependent arising from time immemorial and will continue to be practiced due to the karma of a countless number of Bodhisattvas.
This is my interpretation of Buddhism and may be non-canon to Mahayana. Lest this belief leads anyone to the Buddhist Hell, I place this disclaimer and strive not to be dogmatic about this revelation nor to found a Buddhist sect which enshrines it.