Answer:
Both Jefferson Davis and Abraham Lincoln recognized that "forever" means perpetuity, but they disagreed with the details of what individual should remain forever. In terms of the permanent life of the Confederacy, Davis spoke of perpetuity. "Lincoln insisted that perpetuity, as he advocated for the eternal life of the Union, was" implied, if not expressed, in the basic law of all national governments.
When I was at the debate John’s speech sounded natural, but I could tell it wasn’t premeditated.