‘येयं प्रेते विचिकित्सा मनुष्येऽस्तीत्येके नायमस्तीति चैके। एतद्विद्यामनुशिष्टस्त्वयाऽहं वराणामेष वरस्तृतीयः॥’ ‘Yeyam prete vichikitsã manushye’steetyeka nãyamasteeti chaikeÐ Etadvidyãmanushshista-stvayã’ ham varãnãmesha varastruteeyaha॥ (Katha Upanishad 1/20).
In this third boon, the child Nachiketa requests knowledge of the secret of life after death. Yama Raja thoroughly tested the suitability of the young seeker to receive this profound knowledge. Nachiketa passed the tests admirably, so Yama Raja agrees to fulfil his wish.
Now we will discuss the profound knowledge revealed by Yama Raja, which forms the main message of the Katha Upanishad and which encompasses the whole of spiritual wisdom or brahmavidya.

KNOWING THE FORM OF ATMA
There are many differences of opinion on what happens when a person dies. One of these is related to the separate existence of the atma. Does the atma exist after the death of the body? Some say no. They reason that when a flame is extinguished the light does not remain. They say that this body is itself the atma; the feelings of happiness and misery are associated with the body; and so there is no reason to believe that the atma is separate from the body. In other words, this means that a mixture of pruthvi (earth), jal (water), tej (light), vayu (wind), akash (space) and other elements in certain proportions and ways leads to the ‘birth’ of an atma. Then, with the death of the body, the atma also perishes. So, the atma does not exist after death.
So, Nachiketa requests, “O Yama Raja, please clarify on this issue.”
The reply Yama Raja gives is a defining revelation in philosophy.

ETERNAL EXISTENCE
Yama Raja replies, ‘न जायते म्रियते वा विपश्र्चिन्नायं कुतश्र्चिन्न बभूव कश्र्चित्‌। अजो नित्यः शाश्वतोऽयं पुराणो न हन्यते हन्यमाने शरीरे॥’ – “Na jãyate mriyate va vipaschinnãyam kutaschinna babhoova kaschit Ð Ajonityaha shãshvato’yam purãno na hanyate hanyamãne sharire॥’ – ‘This luminous atma which possesses a variety of knowledge is not born and nor does it die. There is no creator of this atma. It is unborn. Everlasting. Immortal. Ancient. Also, it is हन्यमान – ‘hanyamãna’, that is although it lives in a perishable body, when the body perishes, it never perishes’ (Katha Upanishad 2/18).
Further emphasizing the immortality and imperishability of the atma, Yama Raja says, ‘हन्ता चेन्मन्यते हन्तुं हतश्र्चेन्मन्यते हतम्‌। उभौ तौ न विजानीतो नायं हन्ति न हन्यते॥’ “Hantã chenmanyate hantum hataschenmanyate hatam! Ubhau tau na vijãneeto nãyam hanti na hanyate
“If a slayer believes that ‘I have slain this atma’ or if the atma believes that ‘I have been slain by someone’, then both have a wrong understanding. Since, this atma does not slay anyone and is not slain by anyone” (Katha Upanishad 2/19). This principle is reiterated in the Bhagavad Gita, with a few word changes: ‘न जायते म्रियते वा कदाचिन्नायं भूत्वा भविता वा न भूयः। अजो नित्यः शाश्वतोऽयं पुराणो न हन्यते हन्यमाने शरीरे॥’ – ‘Na jãyate mriyate vã kadãchinnãyam bhutvã bhavitã vã na bhuyahaÐ Ajo nityaha shãshvto’yam purãno na hanyate hanyamãne sharire॥’ (Gita 2/20). ‘य एनं वेत्ति हन्तारं यश्र्चैनं मन्यते हतम्‌। उभौ तौ न विजानीतो नायं हन्ति न हन्यते॥’ – ‘Ya enam vetti hantãram yaschainam manyate hatamÐ Ubhau tam na vijãneeto nãyam hanta na hanyate॥ (Gita 2/19).

ANALOGY OF THE CHARIOT AND CHARIOTEER
आत्मानं रथिनं विद्धि – ‘Ãtmãnam rathinam viddhi’ – ‘Understand the immortality of the atma.’ Now, Yama Raja explains the separate nature of the body, indriyas (semses) and antahkaran (mind, intellect, ego). He uses the analogy of a chariot and its driver to clearly explain the distinct identity of each. He says, ‘आत्मानं रथिनं विद्धि शरीरं रथमेव तु। बुद्धिं तु सारथिं विद्धि मनः प्रगहमेव च॥ इन्द्रियाणि हयानाहुíवषयांस्तेषु गोचरान्‌। आत्मेन्द्रियमनोयुक्तं भोक्तेत्याहुर्मनीषिणः॥’ – “Ãtmãnam rathinam vidhi shariram rathameva tu Buddhim tu sarathim viddhi maraha pragahameva cha॥ Indriyãni hayãnãhurvishayãnsteshu gocharãn Ãtmendriyamanoyuktam bhoktetyãhurmaneeshinaha॥ – ‘O Nachiketa! This body is the chariot and this atma is its owner, the charioteer. The buddhi is its driver. The mind is its reins. The indriyas are the horses pulling the chariot. The objects of taste, touch, etc. are its path. Thus, the atma uses the indriyas and anthkaran as a means to enjoy worldly pleasures. Understand in this way’ (Katha Upanishad 3/3-4).
So, the owner is separate from the chariot, driver, horses, reins, path and everything else. He is called the master of the chariot. Similarly, this atma is totally different from body, indriyas, antahkaran and other things, and is the master, or head, of them all.
This analogy clearly describes the form of the atma. The existence of the atma, its immortality, its unchanging nature, its separateness from the body, and its other qualities are unique features of Sanatan Dharma philosophy. And this knowledge is available to us through the Katha Upanishad. For thousands of years this wisdom has been taught; it has not required any change or improvement. It is truly an eternal principle. As times passes, this ancient wisdom of India is gradually being realized by all to be the best and most modern wisdom of all. This is the power of the Upanishadic principles. Those who do not understand this wisdom will stray further from the truth and lose all strength.
That is why, Bhagwan Swaminarayan repeatedly consolidated the knowledge of the form of the atma among his devotees.
In Vachanamrut Sarangpur-12 he says, “Once a person has clearly understood the distinction between the body and the atma, it cannot be forgotten.... Also, childhood, youth, old age, stoutness, thinness, birth and death are all aspects of the body; so, they should never be thought of as belonging to the atma. On the other hand, being uncuttable, being unpierceable, not aging, being immortal, being the embodiment of jnan, being the embodiment of bliss, and being characterized by eternal existence are all aspects of the atma; they should in no way be considered to belong to the body. Instead, those attributes should be understood to belong to the atma.”
Thus, even after death (of the body), the atma does not perish. It continues to exist. This is the first principle explained by Yama Raja.

KNOWLEDGE OF THE FORM OF PARAMATMA
Another point of discussion about matters after death is whether or not there is a controller over the atma. After death, does anyone control the destiny of the atma? Is there a higher entity than the atma which is liberated from the body and the cycle of births and deaths? Or is there no such entity? Death means that mukti or liberation has been attained. To whom should one offer worship, upasana, even in liberation? And what is the need for this?
Nachiketa requested Yama Raja to clearly explain. The answer by Yama Raja describes the form of Paramatma.

ETERNAL EXISTENCE OF PARAMATMA
First, Yama Raja explains that just, like the atma, Paramatma exists eternally: ‘नित्यो नित्यानां चेतनश्र्चेतनानामेको बहूनां विदघाति कामान्‌’ – ‘Nityo nityãnãm chetaneshchetanãnãmeko bahunãm vidadhãti kãmãn’ – ‘Paramatma is eternal and is superior even to the eternal atmas. That Paramatma is animate and so is different from all that is inanimate. It is beyond even the animate atmas. There is only one Paramatma, yet is able to fulfil the wishes of all’ (Katha Upanishad 5/13).
Thus, Yama Raja undermines the arguments of atheists. Then Yama Raja begins to describe the other qualities of Paramatma.

FOREVER THE CONTROLLER OF ALL
Yama Raja describes that Paramatma is the controller of all.
वर्इशानो भूतभव्यस्य – ‘Ishãno bhootbhavyasya’ – ‘This Paramatma is the controller of all that is happening, has happened and is yet to happen’ (Katha Upanishad 4/12-13). That is, Paramatma controls the destiny of all who assume a physical body, even before birth and also after death.