The Christian Afterlife - or Prelife - and the Judaic Olam Ha Ba ('The World To Come') conflate back to Plato's 'Theory of Forms'.
The theory of Forms The motivation for Plato’s extreme realism is dissatisfaction with what purports to be knowledge of the world around us, where everything is imperfect and changeable. How can we know what tallness is when a tall person is short next to a tree? Or what redness is when an apple that appears red in daylight looks black in the dark? Such things, Plato concludes, are the objects not of knowledge but of opinion or conjecture. What is known must be perfect, eternal and unchanging, and since nothing in our everyday experience (in the ‘realm of becoming’) fits this description, there must be a transcendent ‘realm of being’ where there are perfect and unchanging models or paradigms. These are what Plato calls ‘Forms’ or ‘Ideas’, and it is by virtue of imitating or copying them that things in our experience are the way they are. So, for instance, it is by copying the Form of Justice that all particular just actions are just.
And how, we may wonder, do we gain knowledge of these transcendent Forms, if all that is available to us through our senses is poor imitations or copies?
Plato’s surprising answer is that we must have come to know the Forms when we were in some earlier state and that what we are engaged in now is a process not of learning but of recollection. On this basis Plato develops a thoroughgoing dualism, in which our immortal souls exist prior to occupying physical bodies. It is the process of embodiment that encumbers the soul and causes it to forget the knowledge that it gained from previous direct contact with Forms in the realm of being.
Compare this with Judeo-Christian idea of an immortal life we will have in our afterlives that is quite similar to Plato's transcendent 'Realm of being' where there are perfect and unchanging models or paradigms. In this imperfect 'realm of becoming' we indulge in sins, or any emcumbering of the soul, making us forget the knowledge and existence prior. But all is well! We will return to the unchanging transcendent 'realm of forms' after death.
This world is a Plato's Cave
Plato’s cave
Plato’s complex and many-layered conception of knowledge and truth is illustrated by the most famous of the many images and analogies he used: the Allegory of the Cave. The essence of the story, which appears in his greatest and most influential work, The Republic, is as follows:
‘Imagine you have been imprisoned all your life in a dark cave. Your hands and feet are shackled and your head restrained so that you can only look at the wall straight in front of you. Behind you is a blazing fire, and between you and the fire a walkway on which your captors carry statues and all sorts of objects. The shadows cast on the wall by these objects are the only things you and your fellow prisoners have ever seen, all you have ever thought and talked about.
Now suppose that you are released from your shackles and free to walk around the cave. Dazzled at first by the fire, you will gradually come to see the situation of the cave properly and to understand the origin of the shadows that you previously took to be real. And finally you are allowed out of the cave and into the sunlit world outside, where you see the fullness of reality illuminated by the brightest object in the skies, the Sun.’
As usually interpreted, the cave represents ‘the realm of becoming’ – the visible world of our everyday experience, where everything is imperfect and constantly changing and where ordinary people, symbolized by the chained captives, live a life based on conjecture and illusion. The prisoner released to roam within the cave attains the most accurate view of reality possible within this deceptive world, but it is only when he moves outside the cave, into ‘the realm of being’, that he comes to a full understanding of the intelligible world of truth. This realm is populated by perfect and eternal objects of knowledge, the Forms, and overarching them all is the Form of the Good, represented by the Sun, which bestows on the others their ultimate meaning and reality. Afterlife is when come out of this cave. We also experience transcendence when we are dreaming.