his intellect, all these with his Atman (Self), and unify his "great Self" with the Self of the rest, the tranquility of Oneness with the Avyaktam and "cosmic Self". Self (Atman) is soundless, touchless, formless, tasteless, scentless, without beginning, without end, imperishable, beyond great, blissful, and when one reveres one's own Self, he is liberated. Such Self-realization is not easy according to Katha Upanishad, Paul Deussen states that verses 1.3.10 to 1.3.13 of Katha Upanishad is one of the earliest mentions of the elements of Yoga theory, and the recommendation of Yoga as a path to the highest goal of man, that is a life of spiritual freedom and liberation. This theory is significantly expanded upon in the second chapter of Katha Upanishad, particularly in the sixth Valli. The theory of Atman, Oneness and Plurality - Fourth Valli The fourth Valli starts by asserting that inner knowledge is that of unity, eternal calmness and spiritual Oneness, while the external knowledge is that of plurality, perishable "running around" and sensory objects. The Katha Upanishad in fifteen verses of the fourth Valli, as well as those the fifth Valli, explains what is Atman, how it can be known, the nature of Atman, and why it ought to be known. For definition, it deploys an epistemic combination of "positive assertions" as well as "exposition by elimination", the latter repeated with, Atman, asserts Katha Upanishad, is the subject of Self-knowledge, the bearer of spiritual reality, that which is all-pervading, inside every being, which unifies all human beings as well as all creatures, the concealed, eternal, immortal, pure bliss. It exists and active when man is in awake-state, it exists and active when man is in dream-state. The empirical reality is the "honey" for the Atman, with the honey metaphor repeating "fruit of numerous karma flowers in the valley of life" doctrine found in other Upanishads, such as in the second chapter of Brihadaranyaka Upanishad. To know Atman, look inward and introspect; to know objects, look outward and examine, states Katha Upanishad. Everything that changes is not Atman, that which was, is, will be and never changes is Atman. Just like a baby is concealed inside a mother's womb when conceived, Atman is concealed inside every creature, states verse 2.4.8 of Katha Upanishad. Self is the lord of the past, the lord of the now, and the lord of the future. Self is eternal, never