Humans are, in essence, immortal souls or spirits that temporarily inhabit physical bodies. The afterlife is what happens to the soul when it is separated from the body (i.e., when the body ceases to function after death). Christianity and Islam teach that the soul will end up either in paradise or in eternal torment. In contrast, Buddhism and Hinduism teach that a person is reincarnated, acquiring a new body whose status, importance, and comfort depend on the righteousness of prior lives.
There is no credible evidence of a mind existing without a physical brain. Although some people (mediums) have claimed to observe the actions of ghosts or to be able to communicate with those who have “crossed over” to the spirit world, none of these claims have ever been empirically validated. There are also accounts of “near-death experiences”, after which people report having seen bright lights and tunnels, and visions of departed loved ones. Again, there is no evidence that the visions induced by near-death experiences are any different from those that occur during other brain states, such as while dreaming or under the influence of drugs.
The world around us is often very unfair – for instance, bad people benefit from their evil deeds, while good people get sick and die. Having an existence beyond our current lives and physical bodies, whether re-incarnation or eternal paradise/damnation, satisfies our sense of justice. However, beyond the appeal of wishful thinking, the only support for this proposition comes from various sacred texts.
Absent any evidence that consciousness can exist outside the physical realm, it is reasonable to conclude that the afterlife is a human construct, invented to alleviate fear of death and to help explain the paradox of God‘s purported benevolence and omnipotence given the existence of “evil” in the world.