nāntaḥ-prajñam, na bahiṣ prajñam, nobhayataḥ-prajñam na prajnañā-ghanam, na prajñam, nāprajñam; adṛṣtam, avyavahārayam, agrāhyam, alakṣaṇam, acintyam, avyapadeśyam, ekātma-pratyaya-sāram, prapañcopaśamam, śāntam, śivam, advaitam, caturtham manyante, sa ātmā, sa vijñeyaḥ. - Māṇḍūkya Upaniṣad. One of the standard ways in which Upanishads speak of the supreme reality is by means of telling us what it is not. For example in the above verse on Turiya,…