This timelessness of the ultimate cause over which the battle at Gettysburg was fought is not lost on Lincoln, and he addresses it in the longest sentence in his speech.
It is rather for us to be here dedicated to the great task remaining before us–that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion; that we here highly resolve that these dead shall not have died in vain; that this nation, under God, shall have a new birth of freedom; and that government of the people, by the people, for the people, shall not perish from the earth. (Lincoln 2235)
extension of the basic principles of that unique experiment, a government “of the people, by the people, for the people,” pushed beyond the limits that its eighteenth-century founders had established to a more open and inclusive embrace of democratic equality. (Kaplan 351)