The Purpose of a Constitution
umair haque

Actually, the purpose of the US Constitution is provided in the Preamble to same: 
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defense, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.

Let’s not confuse the Declaration of Independence with the Constitution. I take no position on the rest of this article, in part because I think conflating the two documents results in very questionable reasoning.