The single most famous sentence in American government is just an introduction. The Constitution's Preamble grants no powers at all, yet it says who the whole thing is for, and why.
A preamble is the introductory statement of a document that explains its purpose. The Constitution's Preamble is one sentence, beginning We the People of the United States, and laying out the goals of the entire enterprise.
Those goals are sweeping: to form a more perfect Union, establish justice, ensure domestic tranquility, provide for the common defense, promote the general welfare, and secure the blessings of liberty to ourselves and our posterity.
Legally, it is curious. The Preamble grants no power and creates no rights. Courts do not strike down laws for violating it. It is a statement of intent, the mission statement before the operating instructions.
Yet it does crucial work. Those first three words, We the People, settle the question of where authority comes from, and the list of purposes gives every later clause a reason for being. When Americans argue about what the Constitution is for, they are usually arguing about the Preamble.
