Svabhava (Sanskrit: svabhāva; Pali: sabhāva; Chinese: 自性; pinyin: zìxìng; Tibetan: རང་བཞིན, Wylie: rang-bzhin) literally means "own-being" or "own-becoming". It is the intrinsic nature, essential nature or essence of beings. The corresponding concept in Western philosophy is substance theory.
The concept and term svabhāva are frequently encountered in Hindu and Buddhist traditions such as Advaita Vedanta (e.g. in the Avadhūta Gītā), Mahayana Buddhism (e.g. in the Ratnagotravibhāga), Vaishnavism (e.g., the writings of Ramanuja) and Dzogchen (e.g. in the seventeen tantras).
In the nondual Advaita Vedānta yoga text, Avadhūta Gītā, Brahman (in the Upanishadic denotation) is the svabhāva.
The term first appears in the Shvetashvatara Upanishad, as a possible first cause (jagatkāraṇa). There also seems to have been an Indian philosophical position called Svabhāvavada which was akin to naturalism which held that "things are as their nature makes them". It is possible this position was similar to or associated with Carvaka.
Let us look more closely at what Rāmānuja means by the Lord's "nature". If you read his writings, you will find that he uses two distinct yet related words when referring to the nature of Brahman: svarūpa and svabhāva.
In early Theravādin texts, the term "svabhāva" did not carry the technical meaning or the soteriological weight of later writings. Much of Mahayana Buddhism (as in the Prajñāpāramitā Sūtra) denies outright that such a svabhāva exists within any being; however, while in the tathāgatagarbha sūtras, notably the Mahāyāna Mahāparinirvāṇa Sūtra, the Buddha states that the immortal and infinite Buddha-nature - or "true self" of the Buddha - is the indestructible svabhāva of beings, this position is clarified in the Śrīmālādevī Siṃhanāda Sūtra, which directly states that "tathāgatagarbha is not a substantial self, nor a living being, nor ‘fate,’ nor a person."
In the Pāli Canon, sabhāva is absent from what are generally considered to be the earliest texts. When found in later texts (e.g., the paracanonical Milindapañha), it generically refers to state (of mind), character or truth.
In the post-canonical Abhidhamma literature, sabhāva is used to distinguish an irreducible, dependent, momentary phenomenon (dhamma) from a conventionally constructed object. Thus, a collection of visual and tactile phenomena might be mentally constructed into what is conventionally referred to as a "table"; but, beyond its constituent elements, a construct such as "table" lacks intrinsic existence (sabhāva).
According to Peter Harvey, svabhava in the Theravada Abhidhamma is something conditional and interdependent:
"They are dhammas because they uphold their own nature [sabhaava]. They are dhammas because they are upheld by conditions or they are upheld according to their own nature" (Asl.39). Here 'own-nature' would mean characteristic nature, which is not something inherent in a dhamma as a separate ultimate reality, but arise due to the supporting conditions both of other dhammas and previous occurrences of that dhamma. This is of significance as it makes the Mahayana critique of the Sarvastivadin's notion of own-nature largely irrelevant to the Theravada.
The Vaibhāṣika school held that dharmas have a constant essence or inherent nature (svabhāva) which persists through past, present and future. The term was also identified as a unique mark or own characteristic (svalaksana) that differentiated a dharma and remained unchangeable throughout its existence. According to Vaibhāṣikas, svabhavas are those things that exist substantially (dravyasat) as opposed to those things which are made up of aggregations of dharmas and thus only have a nominal existence (prajñaptisat).
Svabhāva is by definition the subject of contradictory ascriptions. If it exists, it must belong to an existent entity, which means that it must be conditioned, dependent on other entities, and possessed of causes. But a svabhāva is by definition unconditioned, not dependent on other entities, and not caused. Thus the existence of a svabhāva is impossible.
...Madhyamaka explains with the four "beyond concepts," which are that something neither exists, nor does not exist, nor both exists and does not exist, nor is beyond both existing and not existing together. These are the four possibilities. What remains? Nothing. Although we are working only in an intellectual way, this can be considered the ultimate conclusion in Madhyamaka. As an analytical method, this is also correct for Dzogchen. Nagarjuna's reasoning is supreme.
The Union of the Sun and Moon (Tibetan: ཉི་ཟླ་ཁ་སྦྱོར, Wylie: nyi zla kha sbyor), one of the 'Seventeen tantras of the esoteric instruction cycle' (Tibetan: མན་ངག་སྡེའི་རྒྱུད་བཅུ་བདུན, Wylie: man ngag sde'i rgyud bcu bdun) which are a suite of tantras known variously as: Nyingtik, Upadesha or Menngagde within Dzogchen discourse, states:
in objects that are objective appearances
this is the non-duality of appearance and emptiness,
Svabhāva is very important in the nontheistic theology of the Bonpo Great Perfection (Dzogchen) tradition where it is part of a technical language to render macrocosm and microcosm into nonduality, as Rossi (1999: p. 58) states:
The View of the Great Perfection further acknowledges the ontological identity of the macrocosmic and microcosmic realities through the threefold axiom of Condition (ngang), Ultimate Nature (rang bzhin) and Identity (bdag nyid). The Condition (ngang) is the Basis of all (kun gzhi) -- primordially pure (ka dag) and not generated by primary and instrumental causes. It is the origin of all phenomena. The Ultimate Nature (rang bzhin) is said to be unaltered (ma bcos pa), because the Basis [gzhi] is spontaneously accomplished (lhun grub) in terms of its innate potential (rtsal) for manifestation (rol pa). The non-duality between the Ultimate Nature (i.e., the unaltered appearance of all phenomena) and the Condition (i.e., the Basis of all) is called the Identity (bdag nyid). This unicum of primordial purity (ka dag) and spontaneous accomplishment (lhun grub) is the Way of Being (gnas lugs) of the Pure-and-Perfect-Mind [byang chub (kyi) sems].
This extreme nondual yoga text shares a lot of common language with the extreme nondual yoga of Atiyoga (Dzogchen) and its standard Tibetan analogue rang-bzhin (Wylie) is employed in The Mirror of the Mind of Samantabhadra, one of the Seventeen Tantras of Atiyoga Upadesha.
ultimate, natureless [rang bzhin med], the state of the nonarising dharmakāya,
the lamp of the teachings, the great light of the dharmakāya
You should understand that the nature of all phenomena is that of the five aspects of Samantabhadra.
What are these? you ask
They are Samantabhadra as nature,
Samantabhadra as adornment,
Samantabhadra as teacher,
Samantabhadra as awareness, and
... the Pratyekabuddhas accede to the absence of a self or independent self-nature (bdag med).