This particular Upanishad deals chiefly with the Invisible Cause and the visible manifestation, and the whole trend of its teaching is to show that they are one and the same, one being the outcome of the other hence no perfect knowledge is possible without simultaneous comprehension of both. The wise men declare that he who worships in a one-sided way, whether the visible or the invisible, does not reach the highest goal. Only he who has a co-ordinated understanding of both the visible and the invisible, of matter and spirit, of activity and that which is behind activity, conquers Nature and thus overcomes death. By work, by making the mind steady and by following the prescribed rules given in the Scriptures, a man gains wisdom. By the light of that wisdom he is able to perceive the Invisible Cause in all visible forms. Therefore the wise man sees Him in every manifested form. They who have a true conception of God are never separated from Him. They exist in Him and He in them. XV The face of Truth is hidden by a golden disk. O Pushan (Effulgent Being)! Uncover (Thy face) that I, the worshipper of Truth, may behold Thee. XVI O Pushan! O Sun, sole traveller of the heavens, controller of all, son of Prajapati, withdraw Thy rays and gather up Thy burning effulgence. Now through Thy Grace I behold Thy blessed and glorious form. The Purusha (Effulgent Being) who dwells within Thee, I am He. Here the sun, who is the giver of all light, is used as the symbol of the Infinite, giver of all wisdom. The seeker after Truth prays to the Effulgent One to control His dazzling rays, that his eyes, no longer blinded by them, may behold the Truth. Having perceived It, he proclaims: "Now I see that that Effulgent Being and I are one and the same, and my delusion is destroyed." By the light of Truth he is able to discriminate between the real and the unreal, and the knowledge thus gained convinces him that he is one with the Supreme; that there is no difference between himself and the Supreme Truth; or as Christ said, "I and my Father are one." XVII May my life-breath go to the all-pervading and immortal Prana, and let this body be burned to ashes. Om! O mind, remember thy deeds! O mind, remember, remember thy deeds! Remember! Seek not fleeting results as the reward of thy actions, O mind! Strive only for the Imperishable. This Mantram or text is often chanted at the hour of death to remind one of the perishable nature of the body and the eternal nature of the Soul. When the clear vision of the distinction between the mortal body and the immortal Soul dawns in the heart, then all craving for physical pleasure or material possession drops away; and one can say, let the body be burned to ashes that the Soul may attain its freedom; for death is nothing more than the casting-off of a worn-out garment. XVIII