If the Self Is Eternal, Why Do We Fear Death?
Nachiketa debates Death himself. Heidegger calls it Being-toward-death.
Katha Upanishad vs Heidegger. Confronting mortality gives life authenticity, but the Katha disagrees on the conclusion: the Self does not end.
A Boy Walks into the House of Death
Vajasravas had promised to give away everything he owned. The Katha Upanishad opens at a Vishvajit sacrifice, the oldest and most expensive of the public Vedic rites, performed sometime in the late Vedic period in a clearing somewhere on the north Indian plain. Smoke rose from the ceremonial fires in the late afternoon air. Priests chanted around the altar. The donor was supposed to give away all his wealth as a public act of generosity.

Vajasravas cheated. He was giving away only the animals that were too old to be worth keeping. Cows that had drunk their last water, eaten their last grass, given their last milk. The cattle stood still in the dust, ribs showing, waiting for priests who would not want them.
His son Nachiketa watched from the edge of the field. He was perhaps twelve or thirteen years old. Something in the boy refused to let the falseness slide. He walked up to his father and asked a simple question.
'To whom will you give me?'
Vajasravas ignored him. He asked again. And again. Finally the father, shamed into fury by his own child in front of the priests, said what he should not have said. 'To Death I give you.'
Nachiketa took the word literally. He walked away from the smoking field and went to the house of Yama, the lord of death, and waited there without food or water for three days. When Yama returned, he was struck by the boy's presence and offered three boons to make up for the three days of neglect. Nachiketa asked first that his father receive peace of mind. Granted. He asked second for the knowledge of the fire sacrifice that leads to heaven. Granted, and Yama named the fire after him. Then the third boon. And here the story breaks open.