It is obvious that our subject fits right into this sphere. Countless volumes have been written on the subject in the past fifty years or so, ranging from those that paint fancifully lurid pictures lacking any credible basis to those that encourage people to plunge headlong into the unknown in order to add exciting new dimensions to their lives. My brief here is to steer a strictly biblical course, and this will be best done by answering seven questions, beginning with the most fundamental of all.