In plain words
If you too, like them, see only with the eyes of flesh, there is then no difference at all between them and you. With the eyes of flesh you cannot behold the principle of the Ātma, which is beyond them. Even the eye of the mind is not permanent. So you must see with the eye of Jñāna. Like a bubble of water, the body is born, grows and wastes away. You are not the body that is born, grows and wastes away. There is One that is never born and never dies. That, and nothing else, is the principle of the Ātma. That, and nothing else, is your true nature.
‘Knowing which, all becomes known....’
You may ask what the Ātma is. The Ātma is beyond the senses, endless, beyond all measure. “Nirguṇaṃ nirañjanaṃ sanātanaṃ niketanaṃ nitya śuddha buddha mukta nirmalasvarūpiṇaṃ.” That principle of the Ātma is in every individual, and in every living being as well. That is the very power of Consciousness. Only when you recognise that power of Consciousness does your birth find its meaning. All the other questions are needless for you. You are asking about worldly matters. Those are all things you should not ask about. Recognise the principle that, once you know it, makes you one who knows all. If you know the principle of the Ātma, you need not know any of these any more.
The eternal one, with no death and no birth, without beginning, middle or end, the One with no beginning, who is not born, does not die, is not slain, the Lord, the Ātma, who stands witness to all.
If you recognise that principle of the Ātma, you will be one who has recognised everything. In this way Yama explained the principle of the Ātma to Naciketas.
‘Satyaṃ vada, dharmaṃ cara’
See, wherever you look in this hall, bulbs are burning. The bulbs are separate, but the current is just one. It goes through the wire, enters the bulbs and gives light. What is the source of this current? That is none other than divine power. In the same way, though the bulbs called bodies are separate, what makes them all shine is the principle of the Ātma itself.