As has been discussed above, the theory of karma is inseparably connected with that of transmigration. The bondage self is born again and again. Its course in saṁsāra is determined by the karmic particles attracted by it in every state of its existence. The theory of rebirth or transmigration of the self explains its continuous identity through a series of existences in three points of time - past, present and future.
In Sarvārthasiddhi, Saṁsāra (world) has been explained thus:
Saṁsārānāma Saṁsāraḥ parivartanam ityārthaḥ.[25]
The world saṁsāra means transmigration, cycle of wandering. The world parivartana means change. The beings go round and round in saṁsāra due to their attachment with the karmic particles. They are called transmigrating beings, being going from birth to birth. The text further states that the attainment of different states of existence of self as a result of fruition of karma is called saṁsāra.[26]
The word saṁsāra is derived from the root sam-sri, which means to 'follow together with' going about walking on wandering, through, 'passing through a succession of states', birth and rebirth of living beings. Thus the world saṁsāra means going or wandering undergoing transmigration, course, passage, passion, through a succession of states, curcuit of mundane existence, transmigration, metempsychosis, the world, worldly illusion.[27] The existence in saṁsāra is the existence in bondage, the very opposite of liberation. The concept of saṁsāra therefore, forms essential strand in the theory of rebirth and karma.
The jīva in saṁsāra is engulfed by desire and aversion, it is because of these desires and aversion that karma clings to jīva and leads him through different states of existence (gatis). Entering into any state of existence, jīva assumes a physical body and gets the senses. Through the senses arise desire and aversion and on account of desire the cycle of existence continues.[28] Thus desire produces karma and karma leads to existence.
The karttikeyānuprekṣā states that the being or self (jīva) leaves one day and assume another body, and afterwards leaves the body also. In this way the self takes and leaves body repeatedly. Thus the traveling of the self tied to false notions and impurities across numerous bodies is called saṁsāra.[29] According to Dhavalā, Saṁsāra is the bundle of such deeds as overwhelm the real nature of the self, the beings travel in four states of existence because of diverse kind of evil deeds.[30] Jiva is in the cycle of existence so long as he associates himself with the activities of mind, body and speech. Freedom from these activities leads to mokṣa.[31]
Saṁsāra is thus a designation of the process of birth and death. Saṁsāra is also sometimes described as five fold change because of the change of matter (dravya), sphere (kṣetra), time (kāla), thought (bhāva) and destiny (bhava). The soul has been in saṁsāra from the beginningless time, in the course of it's journeying through saṁsāra it has accepted and given up innumerable times one by one all the atoms of the universe, all the space point of spheres, all the molecules of time, all the passions and all the destinies including the hells.
At the root of saṁsāra is mithyātva or perversity of outlook which causes the rise of karmic particles and their attraction by the self (jīva). Mithyātva is the root of saṁsāra or the worldly existence.[32] This principle is accepted to Buddhism also. Avidya or ignorance which is another name of mithyātva, is regarded as the main cause of the cycle of birth and death in Buddhism.