There is also a well motivated reason for evangelism. If it is true there is an eternal life available of absolute wonder, it seems supremely selfish to keep news of this to one's self. So if someone sincerely believes they have the secret to eternal life, it makes sense they might try to tell other people about it. Penn Jillette said that if Christians really believe they can get eternal life through Jesus, then they are cowards of they don't at least attempt to tell others.