What is the Hindu understanding of death and rebirth?
"death and rebirth" as per orthodox hindu metaphysics:
Death = the loss of the gross material body [The 'gross material body' is composed of 5 elemental materials: earth, water, fire, air & ether] ---yet the subtle material body is maintained [The 'Subtle material body' is composed of 3 elemental materials: mind, intelligence & false-ego].
There are 8,400,000 species of life forms available to take birth as ---as per the summation of all one's works balanced out with the summation of all one's demerits.
At the time of death, one's next birth is prompted by the summation of all one's Actions + desires and finally one's last thoughts.
One's next birth is inaccordance with the level of sophistication that was cultivated in one's previous life.
Rebirth = Ones next birth is solely the responsibility of the person in question.
Some are born rich and beautiful . . . others are born otherwise . . . in all combinations in all circumstances:
All the possible stratum of passing the times of ones life are exclusive positions/Numbered Seating/fixed-societal platforms IOW, there are only so many Position-vacancies at any time during the course of History; and all the seats are taken by those best situated to fill in the vacancy of ie: poor-man, rich-man, beautiful throphy wife; rice-farmer, taxi-driver, computer-gamer-programer, police-warden, Soldier, politician.
Karma is like a game of Musical-Chairs ---sly presence of mind and ambition increase the odds of staying in the game. But cheating will incurr funcky scenes ---learning to calm ones lusts for petty engrandisements can allow for regulated & peaceful enviroments to cultivated sublime appreciations for the rat-race we intelligent Humans engage in.
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As per Bhagavad-gita:
the definition of the Spirit soul
[the indivisiable individual persona-being-soul which is the very essence of each of us "Living-entities" aka, "Sentient-beings" aka, "jiva-atmas"]
is exclusively elaborated upon to its 'enth-degree.
IE: We are spirit-souls in the material world. Each and every spirit-soul is an indivisiable individual persona.
Each and every spirit-soul is a minisculely tiny part and parcel of the Supreme-Soul [aka, God-Almighty, who is also an indivisiable individual persona who is Un-equaled and self-born and the fountainhead reservior of material & spiritual energies and especially:
God is known by definition as the fountainhead reservior of Personal-Qualities.
As per the Gita: To ensure the integrity of one's soul's destiny, one must know what a 'soul' is, how is preforms actions (karma); how it accumulates 'karmic-payback' (karma-phalam); how it suffers (ugra-karma); how the soul takes repeated births; enjoys the embodiment's sensual senses; karma
The material body and it's sensual stimuli receptors and it's intellect and ability to answer the calls of nature are the same for all beings.
We are individuals in the material world by dint of the seating arrangement in the Theatre-house of life.
Once we are in the seats that our past-karma afforded us ---we are obliged to act accordingly.
This is indeed mundane . . . but that is as good as it gets . . . until, as recommended by Krishna in the Bhagavad-gita, as mercifully benedicted upon the deserving yearning student, as transmitted by the individual wellwishing representative of Krishna "Song of God" to dove-tail ones actions & consciousness & fruits of one's works in devotion to the Supreme-Soul . . . wheater that Supreme-Soul is mysteriously un-known; or if that Supreme-Soul is represented by "Obliged-duties" [aka, Dharma];
or if that Supreme-Soul is represented by "earnest quests".
One must be schooled in the elementary classes before being passed-on to the next higher level of Teachings; and, sometimes the pre-requsite life-lessons are spread-out over a large expanse of time . . . birth after birth.
The first lesson of spiritual-Life is:
"We are not this material body, we are spirit souls in the Material world"