In this excerpt from Abraham Lincoln's Gettysburg Address, the main purpose of the second paragraph of this speech is To demonstrate the importance of the situation.
The Gettysburg Address was issued by Abraham Lincoln, "Four score and seven years ago" eighty-seven years after the Declaration of Independence. The country is facing a Civil War. Lincoln states that the most important principle is that all men are created equal and that the nation lives by this principle. He issues this speech to demonstrate how important the situation is for the nation.