Tathātā
Tathātā is a Buddhist term variously translated as Thusness, Suchness, True Thusness, or True Suchness, referring to the Ultimate Reality, the intrinsic and essential nature of all existences, free from dualistic thinking, conceptualization, and subject–object distinction. It is formless, uncreated, eternal, perfect, unchanging, indestructible, and is the true nature of all phenomena. It represents the genuine reality of existence, which transcends physical forms, physical senses, and intellectual comprehension, indicating a profound insight into the nature of things as they truly are.
Tathātā has a large number of synonyms found in different Buddhist schools, traditions, and scriptures, such as: Emptiness, Reality Realm, True Suchness, Dharma Nature, Dharma Realm, Dharma Body, Nirvana, Vajra, Actionlessness, Dharma Intrinsic Nature, Buddha-nature, Tathagata-Treasure, The True Reality of all phenomena, etc.
Although it is a significant concept in Mahayana Buddhism, it is also used in the Theravada tradition.
The Buddha
The Buddha referred to himself as the Tathāgata, which can mean either "One who has thus come" or "One who has thus gone", and can also be interpreted as "One who has arrived at suchness".Theravada Buddhism
In Theravada, this term designates the nature of existence, the truth which applies to things. According to the Kathavatthu, tathātā is not an unconditioned or un-constructed phenomenon. The only phenomenon which is un-constructed in Theravada is Nibbana.According to Buddhadasa Bhikkhu, tathātā is merely the way things are, the truth of all things: "When tathātā is seen, the three characteristics of anicca, dukkha, and anatta are seen, sunnata is seen, and idappaccayata is seen. Tathātā is the summary of them all – merely thus, only thus, not-otherness."
Mahayana Buddhism
Tathatā in the East Asian Mahayana tradition is seen as representing the base reality and can be used to terminate the use of words. A 5th-century Chinese Mahayana scripture entitled Awakening of Faith in the Mahayana describes the concept more fully:R. H. Robinson, echoing D. T. Suzuki, conveys how the Laṅkāvatāra Sūtra perceives dharmata through the portal of śūnyatā: "The Laṅkāvatāra is always careful to balance Śūnyatā with Tathatā, or to insist that when the world is viewed as śūnya, empty, it is grasped in its suchness."