Tathāgatarbha or Buddha Nature is the idea that there exists in all beings some form of germinal ‘essence’ of Buddhahood. It is a development of the Mahāyāna tradition, though some scholars have traced possible antecedents in the Buddha’s original teaching. It is equated with the ultimate nature of reality, the paramārthasatya, which is characterised by śūñyatā.
A question has been posed as to whether tathāgatagarbha is really a form of substantialism, ātman, soul or self and therefore a nonBuddhist, even anti-Buddhist teaching. Even if it proves to be impeccably Buddhist, it remains questionable what value the traditional notion of tathāgatagarbha holds for dharma practise in the modern world.
Tathāgatagarbha occupies a crucial position in Mahāyāna thought because it is significant both for its conception of the Path and its overview of the ultimate nature of reality. In Indian Buddhism tathāgatagarbha is chiefly expounded in the Tathāgatagarbhasūtra, in large portions of the Śrīmālā and the Mahāyāna Mahāparinirvāṇa Sūtras, and in sections of the Laṅkāvatāra and the Ghanavyūha. Several Tantric texts are devoted to Tathāgatagarbha, as is the long first chapter of the Ratnagotravibhāga, one of the most basic Śāstras of the Mahāyāna traditionally attributed to Maitreya. The extensive commentary to the Ratnagotravibhāga also quotes numerous tathāgatagarbha Sūtras that were subsequently lost.
The literature contains terms used in earlier parts of the canon which are at least partially equivalent to tathāgatagarbha, for example (tathāgata)dhātu, prakṛtishta-gotra and prakṛtiprabhāsvara-citta.
Fundamentally, the notion of tathāgatagarbha denotes what makes the Path and its fruition in Buddhahood possible. Enlightenment would be impossible without some kind of potential to become enlightened. It is no doubt obvious enough, but the actual nature of this potential and the way it is expressed in words presents a number of problems, including a suggestion of substantialism.