The sources and interpretation of the Declaration have been the subject of much scholarly inquiry. The Declaration justified the independence of the United States by listing 27 colonial grievances against King George III and by asserting certain natural and legal rights, including a right of revolution. Its original purpose was to announce independence, and references to the text of the Declaration were few in the following years. Abraham Lincoln made it the centerpiece of his policies and his rhetoric, as in the Gettysburg Address of 1863. Since then, it has become a well-known statement on human rights, particularly its second sentence: