The Kaṭha Upaniṣad tells a story about a boy named Naciketas who meets the God of Death, named Yama. Naciketas is granted three wishes by Yama. To Yama’s surprise, the boy does not ask for worldly riches or great powers. Instead, he wants answers to the kind of questions that only the God of Death can answer: what happens when we die? What is the secret of immortality? Yama pleads for Naciketas to ask for something else, but the boy stands firm. He demands that Yama not renege on his word. Nothing that Yama can say will change his mind. So Yama complies.
To answer Naciketas’s questions, Yama explains that the true hidden nature of reality is that there is only one, all-pervading consciousness called brahman, which is timeless, unchanging and the only non-illusory thing that was and ever will be. And it is this brahman, says Yama, that is also immanent in all living things as ātman, the individual ego or self:
As the single fire, entering living beings, adapts its appearance to match that of each, so the single Self within every being adapts its appearance to match that of each, yet remains quite distinct.
