See the water in my glass. When I throw it out it will evaporate, enter the atmosphere, reach the clouds and then it will become water again. Similarly when consciousness is this body it may be impure and it may be ignorant, but when this body is gone it becomes pure consciousness.
It is not only one life that a man lives but man goes through a series of lives. Sometimes people are born with memories of the past life. Some can talk about their past life and about things that they buried in their past life. They can dig them up and take them out as evidence. There have been cases like that, that´s why it is called rebirth. Man is bound to ask "What is that, which remembers this past life?", "What is that which takes birth again?" and "What is there which guides the action of a person in this life?".
It is the triad of ego, mind and intellect, that travels from one body to other body, from one life to other life. As long as desires remain it takes birth over and over again. The cycle of birth and death continues and the consciousness keeps on changing pots. Conciousness is recycled. Energy moves like that everywhere. There is growth up to a particular point, then decay up to a particular point. Life and death are two ends of the same cord. Life appears, disappears and then reappears.
Most events in this life have no apparent cause in this life but they have been sown in previous lives. And if you were told the story of your past life then you could see many causes of the tendencies in your present life. It is difficult to find out the story of your past life because you need somebody who can describe what kind of person you were in your last life, how you lived, and what happened. But some people who are able to look into the future can also look into your past lives.
Rebirth as an animal
As long as one works only in the lower three chakras, one does not deserve to have a human birth. If all your life you have been working with your animal instincts, going around only three chakras, food, sleep, sex, a little bit of shelter and a little bit of authority over some people, then it is better you take birth as an animal. Animals have a particular rhythm in which there is a season for this and a season for that. Because in animal life you cannot avoid dharma, dharma is automatically inside you and by following dharma you evolve from animal into man again.
Merging into the source
As long as there are attachments, likes and dislikes, ego continues for the fulfillment of desires. As long as there are desires, individual consciousness needs to be separated from cosmic consciousness and the cycle of birth and rebirth continues. Only when all desires are fulfilled and you don't need to do anything, then comes the desire to become one with the source and then comes true knowledge (gyana). By true knowledge you get illumination and become light, and then you merge into the source.
Once you have merged in the source, your existence is completely lost. Like a drop merges into the ocean and becomes the ocean, individual consciousness merges into the cosmic consciousness and can not brought back. After Jesus became one with the cosmic consciousness you cannot bring him back. If he remained Jesus Christ after merging into god, then there would be the duality of god and Jesus Christ. He may appear to you in a vision but that vision is created by you. Suggestion has the power to make you see Jesus Christ but that will not be the Christ who became one with god.