This 2007 American film by Jerome Bixby is a dialogue-based dramatization of a story by Gordon R. Dickson about a man claiming to be a 14,000 year old caveman. While his friends/former colleagues initially believe that John is pulling their legs and go along for the ride just for fun, they eventually begin to believe that what he says might be true. This causes anger in several of his guests as they are forced to question the validity of the things they have always believed to be absolute truths.
Questions are raised about the validity of both science and religion. Things that are thought to be absolute truths one day may be refuted the next, replaced by new beliefs. People want something that they can believe in and when it seems that one’s comforting belief may be taken away, a person can have irrational, even violent reactions.
I have had discussions about belief with my son, who is, in my opinion, one of the wisest people I have known, although he is only 23 years old. He said that while he has certain spiritual ideas which he on some occasions holds to be true and on other occasions hopes are true, in general he feels that the only way to be a true scientist and a true seeker is to conduct oneself as an agnostic. Thus, one does not reject possibilities, nor embrace anything as absolute. One is always open to discovery and change.
As to the nature of questions such as life, death, and salvation of the soul should there be a soul, we are not in a position to know the absolute truth in these matters. This being the case, it is best to keep an open mind and an open heart. We must, as Dr. Martin Luther King Junior said, learn to disagree without becoming violently disagreeable.