There is one thing that is certain in this lifetime: eventually we all must die. A belief in the cyclical reincarnation of the soul is one of the foundations of the Hindu religion. Death is viewed as a natural aspect of life, and there are numerous epic tales, sacred scriptures, and vedic guidance that describe the reason for death's existence.
The rituals that should be performed surrounding it and the many possible destinations of the soul after departure from its earthly existence. While the ultimate goal is to transcend the need to return to life on earth, all Hindus believe they will be reborn into a future that is based primarily on their past thoughts and actions.
Most of the Hindus believe in the cycle of birth, death and rebirth, which is called 'Samsara'.'Samsara' or the doctrine of rebirth is also known as the theory of reincarnation or of transmigration of the soul. This doctrine is considered to be a basic tenet of Hinduism. According to doctrine of rebirth, differences between individuals, even at the time of their birth are due to their past karma i.e. actions done in the past birth. For example if one child is born healthy while another is handicapped or blind, the differences are attributed to their deeds in their previous lives. Those who believe in this theory reason that since all actions may not bear fruit in this life, there has to be another life for facing or reaping the consequences of one's actions.
Death, according to Hinduism, is a series of changes through which an individual passes. Hinduism speaks of the four courses that men follow after death. The first, called devayana, way of the gods, is followed by spiritually advanced souls who lead an extremely pure life, devoting themselves to wholehearted meditation on Brahman, but who have not succeeded in attaining complete Self-knowledge before death. They repair to Brahmaloka, the highest heaven, and from there in due course attain liberation. The second course, known as pitriyana, way of the fathers, is followed by ritualists and philanthropists who have cherished a desire for the results of their charity, austerity, vows, and worship. Following this path, they repair to Chandraloka, the lunar sphere, and after enjoying immense happiness there as a reward for their good actions, they return again to earth since they still have earthly desires.
The third course, which leads to hell, is followed by those who led an impure life, performing actions forbidden by the scriptures. They are born in sub-human species. After expiating their evil actions, they are again reborn on earth in human bodies. The fourth course is for those who are extremely vile in their thoughts and actions. They are reborn again and again as insignificant creatures such as mosquitoes and fleas. Eventually, after the expiation of their evil actions, they too return to human bodies on earth. When a soul assumes a human body, it takes up the thread of spiritual evolution of its previous human birth and continues to evolve toward Self-knowledge. According to Hinduism, all souls will ultimately attain Self-knowledge.
The moral energy of a particular moral act bears fruit automatically in the next life, manifested in one's class, disposition, and character. Hindu texts also prescribe a number of activities, such as pilgrimages to holy places and acts of devotion that can wipe out the effects of bad karma. Such positive actions are sometimes referred to as "good karma." Some versions of the theory of karma also say that morally good acts have positive consequences. According to Hinduism, the traditions and the elders used to say that a person with perfect humanity and divinity will not have more than one birth. The people who have not been in perfection towards his life habits usually have another birth. This was said to happen 7 times. The person's life was fixed by god as per his behaviour in his previous birth. The philosophy according to Hinduism about rebirth was the mistakes you have done in previous birth can be covered in rebirth and get a perfect human life.
Derk Bodde states that humans have two souls: the hun and the p'o. The hun is the soul that leaves the body but is later compelled to return by a family member. The p'o eventually makes its way to the underworld and represents the dead's raw energy. In Chinese religion, reincarnation does occur: the dead are absorbed into the earth for a period of time and then returned always into the same family as a newborn." Every birth seemed to be the reincarnation of a forbear." Spiritualism combined elements from a variety of different religions, but their primary focus was "scientifically" proving survival after death through direct communication of mediums. While Spiritualists chose not to subscribe to a number of Christian doctrines, including the last judgment and the resurrection of the physical body, they did believe in the continuation of the personality after death, which was considered to be reborn in a spiritual body." At death the soul, which is composed of a sort of subtle matter, withdraws itself and remains near the earth plane for a period of time. After this, it advanced in knowledge and moral qualities and proceeds to a higher plane, until it eventually reaches the sphere of pure spirit."
Moksha is that stage in the life of a human being when one cuts across all the shackles of senses and the mind. Unless we gain absolute control over the five senses and the mind... we cannot achieve Moksha in this life. Gaining absolute control over the senses and the mind is a complex process. One has to diligently take control of all the senses one by one and the moment we establish absolute control over all the five senses... controlling mind is easy to achieve! Our five senses help us live the physical manifest form of us. They have got nothing to do with our true inner self... our soul atman within us.
The Common word used for the doctrine of rebirth is 'Punarjanam'. In Sanskrit 'Punar' or 'Puna', means, 'next time'or 'again' and 'Janam' means 'life'. Therefore 'Punarjanam' means 'next life' or 'the life hereafter'. It does not mean coming to life on earth again and again as a living creature. If one reads many of the references to Punarjanam in Hindu Scriptures besides the Vedas, keeping the life in the hereafter in mind, one gets the concept of the next life but not of rebirths or of life again and again.
This is true for several quotations of the Bhagvad Gita and Upanishad which speak of Punarjanam.This concept of repeated births or of cycle of rebirth was developed after the Vedic period.
This doctrine was included by humans in subsequent Hindu scriptures including the Upanishad, Bhagvad Gita and the Puranas in a conscious attempt to rationalize and explain the differences between different individuals at birth and the different circumstances in which people find themselves in, with the concept that Almighty God is not unjust.
So to say that since God is not unjust the inequalities and differences between people are due to their deeds in their past lives.