Tathātā in the context of "Dharmadhatu"

Vairocana ("The Sun", "Solar" or "Shining" in Sanskrit), also known as Mahāvairocana (Great Sun), is a major Buddha from Mahayana and Vajrayana Buddhism. He is often compared to the Sun, because both bestow their light impartially upon all beings. However, unlike the Sun, whose light can be blocked, and which disappears at night, Vairocana's light is omnipresent, impossible to block, and shines eternally. Hence, he is called the "Great Sun". In East Asian Buddhism, Vairocana is called "大日如來" (Great Sun Thus Come One) or "毘盧遮那佛" (Vairocana Buddha).

In Mahayana and Vajrayana Buddhism, Vairocana is the Dharma-Body of all Buddhas (Dharma-Body is the true body of all Buddhas, equivalent to the Ultimate Reality), which is formless, omnipresent, self-existent, eternal, indestructible, unable to be defiled, and is the source of all manifestations. The historical Gautama Buddha is one of the emanation bodies of Vairocana Buddha.

The Aṣṭasāhasrikā Prajñāpāramitā Sūtra (Sanskrit: अष्टसाहस्रिका प्रज्ञापारमिता सूत्र; English: The Perfection of Wisdom in Eight Thousand [Lines]) is a Mahāyāna Buddhist sūtra in the category of Prajñāpāramitā sūtra literature. The sūtra's manuscript witnesses date to at least c. 184 BCE – c. 46 BCE, making it among the oldest Buddhist manuscripts in existence. The sūtra forms the basis for the expansion and development of the Prajñāpāramitā sūtra literature. In terms of its influence in the development of Buddhist philosophical thought, P.L. Vaidya writes that "all Buddhist writers from Nāgārjuna, Āryadeva, Maitreyanātha, Asaṅga, Vasubandhu, Dignāga, down to Haribhadra concentrated their energies in interpreting Aṣṭasāhasrikā only," making it of great significance in the development of Madhyāmaka and Yogācāra thought.

The sūtra deals with a number of topics, but is primarily concerned with the conduct of a bodhisattva, the realisation and attainment of the Perfection of Wisdom as one of the Six Perfections, the realisation of thusness (tathātā), the attainment of irreversibility on the path to buddhahood (avaivartika), non-conceptualisation and abandonment of views, as well as the worldly and spiritual benefit of worshipping the sūtra.