By using these similies of fire and air, the teacher tries to show Nachiketas the subtle quality of the great Self, who, although one and formless like air and fire, yet assumes different shapes according to the form in which It dwells. But, being all-pervading and unlimited, It cannot be confined to these forms; therefore it is said that It also exists outside all forms. XI As the sun, the eye of the whole world, is not defiled by external impurities seen by the eyes, thus the one inner Self of all living beings is not defiled by the misery of the world, being outside it. The sun is called the eye of the world because it reveals all objects. As the sun may shine on the most impure object, yet remain uncontaminated by it, so the Divine Self within is not touched by the impurity or suffering of the physical form in which it dwells, the Self being beyond all bodily limitations. XII There is one ruler, the Self of all living beings, who makes the one form manifold; the wise who perceive Him seated within their Self, to them belongs eternal bliss, not to others. XIII Eternal among the changing, consciousness of the conscious, who, though one, fulfils the desires of many: the wise who perceive Him seated within their Self, to them belongs eternal peace, not to others. XIV They (the wise) perceive that indescribable highest bliss, saying, This is That. How am I to know It? Does It shine (by Its own light) or does It shine (by reflected light)? XV The sun does not shine there, nor the moon, nor the stars; nor do these lightnings shine there, much less this fire. When He shines, everything shines after Him; by His light all is lighted. Part Sixth I This ancient Aswattha tree has its root above and branches below. That is pure, That is Brahman, That alone is called the Immortal. All the worlds rest in That. None goes beyond That. This verily is That. This verse indicates the origin of the tree of creation (the Samsara-Vriksha), which is rooted above in Brahman, the Supreme, and sends its branches downward into the phenomenal world. Heat and cold, pleasure and pain, birth and death, and all the shifting conditions of the mortal realm--these are the branches; but the origin of the tree, the Brahman, is eternally pure, unchanging, free and deathless. From the highest angelic form to the minutest atom, all created things have their origin in Him. He is the foundation of the universe. There is nothing beyond Him. II Whatever there is in the universe is evolved from Prana and vibrates in Prana. That is a mighty terror, like an upraised thunderbolt. They who know That become immortal. III From fear of Him the fire burns, from fear of Him the sun shines. From fear of Him Indra and Vayu and Death, the fifth, speed forth.