According to Hindu philosophy, sansara is the endless cycle of birth, death and rebirth. The periodic emergence, dissolution and re-emergence of all existences has been described in shlokas from 8.17 to 8.19 of the Bhagavad Gita.
As stated in various shlokas of the second chapter of this religious classic, every being in the universe is a distinct soul (jeevatman – the embodied soul or the self). These souls are eternal and indestructible. But the physical bodies in which these souls reside, are perishable. The soul does not die when the body dies. The soul changes his bodies just like one changes his clothes. When the soul leaves one body and takes another, he takes the mind and the senses of that body along with it, to the other body.
Rebirth is the law of nature. One who has taken birth is bound to die ; and after death, he is sure to take birth again. One can, however, be freed from this painful continuation of repeated births through sincere spiritual practices. Those who are perfected on the path of yoga – gyan yoga, karma yoga and bhakti yoga – escape from the cycle of birth and death i.e. they are not born again. In such a state of being, the ego created by ignorance, attachment and arrogance dissolves and the embodied soul realises his identity with the Supreme Self. Ignorance affects the individual soul and not the Supersoul. Hence, in the state of perfection, feeling of separateness vanishes. One is freed from the cycle of birth and death. On the other hand, those who are not perfected in yoga, they are born again and again.
Fate of those who take to yoga with faith but fail to achieve perfection has been discussed in shlokas from 6.37 to 6.45. It has been assured that they do not suffer either in this world or in the life hereafter. Such a sincere but imperfect practitioner of yoga attains heaven and dwells there for long. Thereafter, he takes birth in a pure and prosperous family or in the family of enlightened persons. Due to experiences of the previous lives, he gets automatically attracted to yogic practices and regains the impressions of yogic consciousness cultivated in those lives. And with that he strives again for attaining the perfection. When such a yogi who has cleansed himself of all sins through the practice of many lives, strives earnestly for further progress, soon he attains to the supreme goal.
Rebirth of the soul is also impacted by the modes of material nature (gunas). It has been stated in shlokas 14.14 and 14.15 that when a soul leaves the body under the dominance of the mode of goodness (sattva guna), he then attains to the pure worlds of those who know the Highest. He who dies in the supremacy of the mode of passion (rajas guna), is born among the ones attached to action. And he who dies under the influence of the mode of ignorance (tamas guna), is born to the deluded. It has further been stated in shloka 14.18 that those who are established in the mode of goodness attain the heaven, those who abide in the mode of passion remain on earth ; and the ones steeped in the disgusting tendencies of the mode of ignorance fall into the hell.
The importance of the state of one’s mind at the time of his death has been emphasised in shlokas from 8.5 to 8.16. Whatever state of being, one thinks of while giving up his body ; he attains that state because he ever remains absorbed in contemplation thereof. Therefore, the one who, at the time of death, gives up his body thinking of the Supreme alone, attains to the status of the Supreme. Having reached there, he does not take birth again in this impermanent world, full of miseries, because he has reached the highest perfection. The phrase ‘ever remains absorbed in contemplation thereof’ implies that what determines one’s next life is not only the thought of the last moment but the persistent endeavour of the whole of his life.
In shlokas from 8.23 to 8.26 Krishna has described the paths and periods departing at which one is born again ; and also the paths and periods departing at which one is liberated.
The fate of the divine and the demoniac persons has been described in shlokas from 16.19 to 16.22. It has been stated that the demoniac, the evil doers, constantly take birth in inauspicious demoniac species of life and go to the lowest state. On the other hand, those who have overcome lust, anger and greed ; they reach the highest state.
All these are the factors which influence one’s future state of being. To put the whole concept in contemporary language, it can be said that lessons learnt from the experiences of this life and also the previous lives are recorded in the soul, on a permanent basis. This underlying database, which remains dormant, is carried by the soul from one body to another. These latent impressions of the soul form the basis of one’s initial start in the new life.
To conclude, one’s thoughts and deeds of the past have determined his present birth ; and his present thoughts and actions will decide his future life.