religions, ancient and medieval scholars. The Brihadaranyaka Upanishad is among the earliest extensive discussions of the Hindu concept of dharma, karma and moksha (liberation from sorrow, freedom, emancipation, self-realization). Paul Deussen calls it, "unique in its richness and warmth of presentation", with profoundness that retains its full worth in modern times. Max Muller illustrated its style as follows, Isha Upanishad The Isha Upanishad is found in the White Yajurveda. It is one of the shortest Upanishads, embedded as the final chapter of the Shukla Yajurveda. A key scripture of the Vedanta sub-schools of Hinduism, its name is derived from "hidden in the Lord (Self)". The Isha Upanishad discusses the Atman (Soul, Self) theory of Hinduism, and is referenced by both Dvaita (dualism) and Advaita (non-dualism) sub-schools of Vedanta. It is classified as a "poetic Upanishad" along with Kena, Katha, Svetasvatara and Mandukya Upanishads. Taittiriya Upanishad The Taittiriya Upanishad is found in the black Yajurveda. It is the seventh, eighth and ninth chapters of Taittiriya Aranyaka, which are also called, respectively, the Siksha Valli, the Ananda Valli and the Bhrigu Valli. The Taittiriya Upanishad includes verses that are partly prayers and benedictions, partly instruction on phonetics and praxis, partly advice on ethics and morals given to graduating students from ancient Vedic gurukul (schools), partly a treatise on allegory, and partly philosophical instruction. The text offers a view of education system in ancient India. It also includes sections on ethics and invocation for one's personal development. Max Muller translates the text's tenth anuvaka, for example, as an affirmation of one's Self as a capable, empowered blissful being. The tenth anuvaka asserts, "I am he who shakes the tree. I am glorious like the top of a mountain. I, whose pure light (of knowledge) has risen, am that which is truly immortal, as it resides in the sun. I (Soul, Self) am the treasure, wise, immortal, imperishable. This is the teaching of the Veda, by sage Trisanku." Katha Upanishad The Katha Upanishad is found in the black Yajurveda. The Upanishad is the legendary story of a little boy, Nachiketa – the son of sage Vajasravasa, who meets Yama – the Indian deity of death. Their conversation evolves to a discussion of the nature of man, knowledge, Ātman (Soul, Self) and moksha (liberation). The Kathaka Upanishad is an important ancient Sanskrit corpus of the Vedanta sub-schools. It asserts that "Atman (Soul, Self) exists", teaches