20 ! read the preamble to the united states constitution. we the people of the united states, in order to form a more perfect union, establish justice, insure domestic tranquility, provide for the common defence, promote the general welfare, and secure the blessings of liberty to ourselves and our posterity, do ordain and establish this constitution for the unite states of america. what is the purpose of the preamble? to endow legal authority on those writing the constitution to provide the rules around governing the united states to persuade the king of england to grant the united states independence to inform theirs and future generations of the intent of the constitution