Today when we think of the afterlife we usually think of binary concepts of heaven and hell. We might imagine fluffy clouds, singing choirs of angels, Saint Peter at the heavenly gates, or Satan holding a pitchfork, and the fiery tortures of hell. We also tend to imagine an immediate arrival at either of these destinations after death.
In the first century C.E., however, very few of these ideas about the afterlife were operative; but we can begin to see the origins of our present concepts in the beliefs of early Christians.
Prior to the Second Temple period, both Jewish and Greek thought were dominated by the idea that people went to the same space after death and lived a shadowy existence. In the Hebrew Bible this space is called Sheol, and in Greek texts like The Odyssey it is called Hades. Even though everyone was thought to go to the same place after death, death (and along with it Sheol and Hades) was still something that a person would want to avoid for as long as possible
By the Second Temple period, apocalyptic literature had configured separate spaces for persons both before and after the final judgment, based upon different types of earthly behavior. The final judgment, or day of judgment, refers to a future date on which all of the dead will be raised, souls will be reunited with bodies, and all people and nations will be judged by God. 1 Enoch 22 for instance, describes four containers that souls inhabit while they await judgment, each with amenities that befit a person's behavior on earth. This pre-sorting of souls was not random but prefigured one’s ultimate destination after the last judgment. Similarly, in 4 Ezra 7 readers are confronted with “two ways,” one that is wide and easy and leads to destruction and another that is narrow and difficult and leads to paradise.
During this same period, the influence of Greek philosophy was widening. Stories like Plato's myth of Er, in which the wicked and righteous souls journey to different spaces after death, contributed to the idea of a differentiated afterlife that was emerging in apocalyptic thought (Plato, Republic 10.614-615). Similar to Jewish apocalyptic literature, Greek visions of the other world tended to focus on the behaviors that a person could reform in their earthly life to avoid an unwanted afterlife either in Hades (Lucian, Menippus 14) or in another far-off space (Plato, Phaedo 107-108).
In our earliest Christian writings in the first century C.E., Paul and the Gospel writers worked within this framework and imagined different spaces for the righteous and the wicked at the last judgment or immediately after death. In the Gospel of Matthew, for example, we find the now-popular image of Peter and the keys to the kingdom of heaven (Matt 16:17-20), although the only “gates” mentioned there are still the gates of Hades.
In Luke’s Gospel we find the punishment of the rich man and the reward of the poor man Lazarus residing with Abraham in comfort after his death (Luke 16). The otherworldly reversal of fates in the story of the rich man and Lazarus mirrors the story of Er in Plato’s Republic in its focus on earthly behavior as opposed to post-mortem fate. But many of the other early depictions of eternal torment are of masses of unnamed sinners (Matt 8:12, Matt 13:42, Matt 13:50, Matt 22:13, Matt 24:51, Matt 25:30; Rev 19:19-21, Rev 20:7-15). The unnamed are still a far cry from our contemporary visions of the afterlife and describe a final judgment that happens at some time in the future, not immediately after death. But these New Testament appropriations of apocalyptic thought later developed into more robust concepts of an afterlife.
In the time of Jesus and the decades that followed, the binary understanding of the afterlife was emerging, influenced by Jewish apocalyptic thought and Greek philosophy. In the late first century C.E. we already see a fusion occurring between these Jewish and Greek concepts in the New Testament Gospels. These new concepts of the afterlife would later be harmonized into the early Christian ideas of heaven and hell that are more familiar today.