Dr K K Aggarwal
It’s the most difficult subject. Firstly, you, must be a believer of rebirth, have faith in Vedas and have some knowledge of Sankhya Philosophy and Advaita Vedanta. You must also understand the concept of unmanifest God and manifest God.
Both Prashna and Chandogya Upanishad answers some of the unanswered questions in modern medicine. What make life reversible with CPR even after hours if the body temperature is low? Why food is considered Brahman in Vedas? How soul travels in the universe? But also raise some questions which are difficult to understand as on today.
6.8.6 तस्य क्व मूलं स्यादन्यत्राद्भ्य्ऽद्भिः सोम्य शुङ्गेन तेजो मूलमन्विच्छ तेजसा सोम्य शुङ्गेन सन्मूलमन्विच्छ सन्मूलाः सोम्येमाः सर्वाः प्रजाः सदायतनाः सत्प्रतिष्ठायथा तु खलु सोम्येमास्तिस्रो देवताः पुरुषं प्राप्य त्रिवृत्त्रिवृदेकैका भवति तदुक्तं पुरस्तादेव भवत्यस्य सोम्य पुरुषस्य प्रयतो वाङ्मनसि सम्पद्यते मनः प्राणे प्राणस्तेजसि तेजःपरस्यां देवतायाम् ॥
tasya kva mūlaṃ syādanyatrādbhy’dbhiḥ somya śuṅgena tejo mūlamanviccha tejasā somya śuṅgena sanmūlamanviccha sanmūlāḥ somyemāḥ sarvāḥ prajāḥ sadāyatanāḥ satpratiṣṭhā yathā tu khalu somyemāstisro devatāḥ puruṣaṃ prāpya trivṛttrivṛdekaikā bhavati taduktaṃ purastādeva bhavatyasya somya puruṣasya prayato vāṅmanasi sampadyate manaḥ prāṇe prāṇastejasi tejaḥ parasyāṃ devatāyām ||
Meaning: Where else, except in water, can the body have its root? O Somya, when water is the sprout, search for fire as the root; when fire is the sprout, O Somya, search for Sat [Existence] as the root. O Somya, Sat is the root, Sat is the abode, and Sat is the support of all these beings. As to how, O Somya, these three deities [fire, water, and earth] enter a body and each becomes threefold, this has already been explained.
O Somya, as this person is dying, his speech merges into the mind, his mind into prāṇa, his prāṇa into fire, and then fire merges into Brahman, the Supreme Deity.
Commentary: Death is an active proves and not a passive process. At the time of death Karmendriyas (speech) merges together as Vakvriti and the same gets merges as Mano Vriti (Gnanendriyas and Mind Intellect Ego and Chitta). This merges into Prana and then Prana merges into Tejas and finally to sat. This explains till the Tejas is there in the body life is reversible. Tejas in Vedic language is the Udana Vayu and in Modern Medicine is the metabolism. Once the Prana Vriti merges into the Sat, we say brain death and irreversible death. In Modern Medicine it is well known that if the Tejas is frozen the period of CPR can be extended.
Now what let us see what happens to Tejas after death
5.10.6: अभ्रं भूत्वा मेघो भवति मेघो भूत्वा प्रवर्षति त इह व्रीहियवा ओषधिवनस्पतयस्तिलमाषा इति जायन्तेऽतो वै खलु दुर्निष्प्रपतरं यो यो ह्यन्नमत्ति यो रेतः सिञ्चतितद्भूय एव भवति ॥
abhraṃ bhūtvā megho bhavati megho bhūtvā pravarṣati ta iha vrīhiyavā oṣadhivanaspatayastilamāṣā iti jāyante’to vai khalu durniṣprapataraṃ yo yo hyannamatti yo retaḥ siñcati tadbhūya eva bhavati ||
Meaning: Having become mist, it changes into clouds. Then from clouds, it becomes rain and falls to the earth. Finally, it grows as paddy, barley, plants, trees, sesame, beans, and so forth. The change from this state is very difficult. Those who eat these things produce children just like themselves.
Commentary: As per Vedas, also as per Chandogya Upanishad as described in this shloka the Sukshma Sharira (the senses and the mind) attached to the soul becomes a mist and clouds. Mist and cloud behaves like a carrier.
It enters through the rains and falls to the earth. In the earth in enters the plant life. So, this Upanishad talks about an intermediate stage between two human lives.
Only when the appropriate human eats the plant, it enters the body through the sperms (or the ova?) to be born again.
Probably this explains why food is called Brahman in Vedas. And destroying food or agriculture is called Brahma Hatya.