everywhere, within and without, it is immortal. This universal, oneness theme is explained by the Katha Upanishad by three similes, which Paul Deussen calls as excellent. Just like one light exists and penetrates the cosmic space, enveloping and clinging to everything and every form individually, the "one inner Self" of beings exists and dwells in all beings, clings to every form and remains still without, states the Katha Upanishad. Just like one air exists and penetrates the world, enveloping and clinging to everything and every being individually, the "one inner Self" of beings exists and dwells in all beings, clings to every form and remains still without. Just like the Sun exists and its nature is not contaminated by the impurities seen by the eyes, the "one inner Self" of beings exists and its nature is pure, never contaminated by the sorrows and blemishes of the external world. Parts of the ideas in these first two similes of Katha Upanishad are of far more ancient origins, and found for example in Book 6, Chapter 47 of Rig veda. That individual is perennially happy, asserts Katha Upanishad, who realizes the Atman is within him, that he himself is the Master, that the inner Self of all beings and his own Self are "one form manifold", and none other. Life is spirit, full of joy. Meaning is Atman, full of perennial peace. "Truly, this is that", once deeply felt and understood by man, is inexpressible highest joy. It is he who realizes this who shines, his splendour shines everything with and by (Anu), the whole world shines by such joy unleashed, such splendour manifested. The theory of Yoga - Sixth Valli The sixth Valli continues the discussion of Karma and rebirth theory, sections of which Max Muller states is possibly interpolated and inserted in a later period. The first five verses of the last section of the Upanishad assert that those who do not know or do not understand Atman return to the world of creation, and those who do are free, liberated. Some unaware of Brahman's essence are naturally inclined to fear God and its manifestation such as nature (fire, lightning, sun), state verses 2.6.2 and 2.6.3 of Katha Upanishad. Those who are aware of Brahman's essence, are awakened to the knowledge, fear no one and nothing, become immortal as with Brahman. The Katha Upanishad, in verses 2.6.6 through 2.6.13 recommends