The Tathāgatagarbha Sūtra is an influential and doctrinally striking Mahayana Buddhist scripture which treats of the existence of the "Tathagatagarbha" (Buddha-Matrix, Buddha-Embryo, Buddha-Essence, lit. "the womb of the thus-come-one") within all sentient creatures. The Buddha reveals how inside each person's being there exists a great Buddhic "treasure that is eternal and unchanging". This is no less than the indwelling Buddha himself.
Sree Padma and Anthony Barber associate the development of the Tathagātagarbha Sūtra with the Mahāsāṃghika sect of Buddhism, and conclude that the Mahāsāṃghikas of the Āndhra region (i.e. the Caitika schools) were responsible for the inception of the Tathāgatagarbha doctrines.
The Tathāgatagarbha Sūtra is considered "the earliest expression of this [the tathāgatagarbha doctrine) and the term tathāgatagarbha itself seems to have been coined in this very sutra." The text is no longer extant in its language of origin, but is preserved in two Tibetan translations and one Chinese translation.
In regard to the Tathāgatagarbha Sūtra and the term Tathagatagarbha A. W. Barber writes:
.....as Alex Wayman, Michael Zimmermann, and I have noted, the original meaning of the term was that one is "already" or primordially Awakened. For example, the Tathagatagarbha Sutra illuminates the matter metaphorically this way: "inside a casting mold there is perfectly formed Buddha; the ignorant see the filth of the mold but the wise know that The Buddha is within."
The Tathagatagarbha Sutra constitutes one of a number of Tathagatagarbha or Buddha-nature Sutras (including the Mahaparinirvana Sutra, the Srimala Sutra, the Angulimaliya Sutra, and the Anunatva-Apurnatva-Nirdesa scripture) which unequivocally declare the reality of an Awakened Essence within each being. The "Tathagatagarbha"/Buddha nature does not, according to some scholars, represent a substantial self (Atman); rather, it is a positive Language expression of "Sunyata" (Emptiness) and represents the potentiality to realize Buddhahood through Buddhist practices; the intention of the teaching of 'Tathagatagarbha'/Buddha nature is soteriological rather than theoretical. This interpretation is contentious. Not all scholars share this view.
Professor Michael Zimmermann, a specialist on the Tathagatagarbha Sutra, writes for instance: 'the existence of an eternal, imperishable self, that is, Buddhahood, is definitely the basic point of the Tathagatagarbha Sutra'. Professor Zimmermann also declares that the compilers of the Tathagatagarbha Sutra 'did not hesitate to attribute an obviously substantialist notion to the Buddha-nature of living beings' and notes the total lack of evident Interest in this Sutra for any ideas of 'Emptiness' (Sunyata): 'Throughout the whole Tathagatagarbha Sutra the term Sunyata does not even appear once, nor does the general drift of the TGS somehow imply the notion of Sunyata as its hidden foundation.
On the contrary, the Sutra uses very positive and substantialist terms to describe the nature of living beings.' Also, Writing on the diverse understandings of Tathagatagarbha Doctrine, Dr. Jamie Hubbard comments on how some scholars see a tendency towards monism in the Tathagatagarbha [a tendency which Japanese scholar Matsumoto castigates as non-Buddhist]. Dr. Hubbard comments:
'Matsumoto [calls] attention to the similarity between the extremely positive Language and causal structure of Enlightenment found in the Tathagatagarbha literature and that of the substantial monism found in the Atman/Brahman tradition. Matsumoto, of course, is not the only one to have noted this resemblance. Takasaki Jikido, for example, the preeminent scholar of the Tathagatagarbha tradition, sees monism in the Doctrine of the Tathagatagarbha and the Mahayana in general …
Obermiller wedded this notion of a monistic Absolute to the Tathagatagarbha literature in his translation and comments to the Ratnagotra, which he aptly subtitled “A Manual of Buddhist Monism” … Lamotte and Frauwallner have seen the Tathagatagarbha Doctrine as diametrically opposed to the Madhyamika and representing something akin to the monism of the Atman/Brahman strain …’
Buddhahood is thus taught to be the timeless, Virtue-filled Real (although as yet unrecognised as such by the deluded being), present inside the Mind of every sentient being from the beginningless beginning. Its disclosure to direct Perception, however, depends on inner Spiritual Purification and purgation of the superficial obscurations which conceal it from view.