Tathata (skt. tathatā तथताChinese 真如, pinyin zhēnrú, W.-G. chen-ju; Tib. de bzhin nyid; kor. 진여, jinyeo; jap. 真如, shinnyo; viet. chân or chơn như; Eng. approx: Soheit or Solchheit) is a term in Buddhism (especially in the Mahāyāna) for the form of true or fundamental reality (but not this reality itself), usually in reference to the aspect of emptiness or essential beinglessness imputed to it.
In the Buddhist tradition it is said of it that it can only be experienced, but not realized linguistically. Who experiences reality in this form, i.e. as it is, has overcome all erroneous knowledge according to Buddhist understanding. The historical Buddha, Siddhartha Gautama, claimed this about himself and therefore also called himself Tathāgata.
The Yogācāra schools, one of the few Buddhist doctrinal traditions that make positive statements regarding Tathata, understand it as a purification of consciousness from any object reference, whereby the factors of existence are to be recognized in their highest sense.
Pure, illusion-free cognition of Tathata is thus equivalent to mere consciousness without grasping, thinking, or the enunciation of meaning. As part of the unconditioned elements (asaṃskṛta-dharma) in the categories of the 100 factors of existence, Tathata is also the condition of the possibility of cognition at all.
A fourth-century analysis fundamental to the Yogācāra schools reads as follows:
"20: All things which are imagined by any imagination constitute the imagined being. This is not existent.
21: The dependent being, on the other hand, is the conception arising from causes. The perfect (being) is its constant freedom from the preceding.
22: Therefore, this is neither different nor not different from the dependent being, like the impermanence etc. As long as this has not happened, the latter is not seen.
23: In view of the threefold essence-lessness of this threefold being, the essence-lessness of all realities has been taught.
24: The first is insubstantial according to the characteristic. The second again, because it has no being of its own. A further essence-lessness results from it,
25: That it (= the third, namely the perfect being) is the highest reality (paramārthaḥ) of the realities. This is also the suchness, because it is so at all times. And it is, moreover, the mere cognition."
The concept of suchness has often been the subject of theoretical disputes within Buddhism. For example, the Japanese Kegon-shū (which, however, itself adhered to the concept of Tathata) criticized the view of the Hossō-shū (Japanese Yogācāra offshoot) that there could be such a thing as objectless consciousness:
This would simply be unconsciousness and therefore could not be a source of experience.
But it was not only in epistemological terms that the concept of tathata proved problematic.
Since also in ontological terms both absoluteness and unconditionality in connection with (eternal) being were attributed to it, and occasionally even an identification of phenomena with the Tathata occurred, some Buddhist doctrinal traditions denied its practicability or validity or the interpretations amounting to such attributions, since this was in contradiction to other, fundamental Buddhist concepts.
Nevertheless, the concept of tathata proved to be impactful within Buddhist philosophical history.
Thus Saichō, founder of the Tendai-shū, in his famous written argument in 817 with the Hossō scholar Tokuitsu (徳一; c. 760-835), argued over the correct interpretation of Buddha-nature and icchantika, and held against Tokuitsu that Buddha-nature belongs to all that exists, since Tathata is, as it were, the essence of all that exists in which it manifests.
Later, Tendai scholars adopted this conception of Tathata in order to make plausible the doctrine of primordial enlightenment (本覺思想, hongaku shisō), according to which every being is already in a state of enlightenment and only needs to realize this state.
The work Shinnyo kan, attributed to Genshin (源信; 942-1017) but written only in the 12th century, was the first of its kind. Century, Shinnyo kan (真如観) elaborates on this and recommends that the reader be aware day and night that he is identical with Tathata.
Kūkai, founder of the Shingon-shū, also used the concepts of Tathata and Buddha nature, which he believed to be the nature of the Dharma body. The Shingon-shūkai was the founder of the Dharma body.