It is important to know that more than half the world believes and accepts reincarnation. The proposition, a very old one indeed, is that we come back to the Earth again and again.
Each time we return, we take on vehicles and bodies which anticipate the vibrations of the Earth; and in the process of incarnating, somehow or other we move towards perfection, towards what Plato called ‘Truth, Beauty and Goodness’.
This process of moving constantly towards perfection involves many cosmic laws - most of all a great cosmic law called karma. Karma and reincarnation are sister doctrines.
If the rod of the caduceus is the staff of life - your life, my life, or the life of animals - then one serpent represents the process, for humans anyway, of reincarnation. Interthreaded with it, there is the proposition of karma.
Karma and reincarnation work together; they are sister doctrines and they produce not only our capacity to incarnate but also to evolve our consciousness.
So we can understand that a life may be devoted entirely to the process of evolving consciousness, or it may be devoted entirely to the act of learning how to control a boisterous physical body.
Then we arrive at the idea that there is a purpose for that particular life, and you cannot accept that without grasping that the rod of life is immortality.
As we incarnate, we are moving towards greater consciousness, and in the end the aim of it all is immortality. I am immortal, so are you. The difference may be that I know that I am immortal - and it makes life much easier to comprehend. If you are immortal, there must be something that goes on and on, irrespective of death and reincarnation.