It was not because it was proposed to establish a new nation, but because it was proposed to establish a nation on new principles, that July 4, 1776, has come to be regarded as one of the greatest days in history. Great ideas do not burst upon the world unannounced. They are reached by a gradual development over a length of time usually proportionate to their importance. This is especially true of the principles laid down in the Declaration of Independence. Three very definite propositions were set out in its preamble regarding the nature of mankind and therefore of government. These were the doctrine that all men are created equal, that they are endowed with certain inalienable rights, and that therefore the source of the just powers of government must be derived from the consent of the governed.

– Pres. Calvin Coolidge speaking on the 150th anniversary of the Declaration of Independence

http://teachingamericanhistory.org/library/document/speech-on-the-occasion-of-the-one-hundred-and-fiftieth-anniversary-of-the-declaration-of-independence/