Why do you think Lincoln connected his Gettysburg Address to the Declaration of Independence?

In it, he invoked the principles of human equality contained in the Declaration of Independence and connected the sacrifices of the Civil War with the desire for “a new birth of freedom,” as well as the all-important preservation of the Union created in 1776 and its ideal of self-government.

Explanation:

It was an important occasion for the Nation to honor those who had given their lives during the Battle of Gettysburg. ... Lincoln was declaring that the United States would continue to fight to preserve the nation that was created by the Founding Fathers who wrote the Declaration of Independence in 1776.

Explanation:

so they can defeat there oppenent

social contract theory basically says that all individuals are born equal, and provided a god given right to consent to be governed. american government is based of this

thomas hobbes and john locke said that we are selfish, individualistic, and constantly at war with each other, therefore we need to be controlled. 

government is defined as the legitimate use of force to control human behavior within territorial boundaries, here comes in hobbes and locke.

hobbes takes the part about controlling human behavior. while locke takes the part of legitimate use of force, since force is not legitimate unless there is consent of the people. 

there are basically 3 goals of the government: 1) maintain order by protecting life and property. 2) providing public goods, those which are typically not provided by the public sector, such as roads and education. 3) promote equality be it political, opportunist or outcome equality.