Final answer:
The Preamble of the US Constitution sets forth the goals of the new government and is based on the authority of the people. Its purposes include establishing justice, ensuring domestic tranquility, and promoting the general welfare.
Step-by-step explanation:
The Preamble is the opening statement of the US Constitution, outlining the goals that the new government seeks to achieve. It is a statement of both the source of the political authority of the Constitution and its purposes. The Constitution rests on the authority of 'We the People,' emphasizing the idea of popular sovereignty, which means that all government power comes from the people. The purposes of the Constitution, as stated in the Preamble, include establishing justice, ensuring domestic tranquility, providing for the common defense, promoting the general welfare, and securing the blessings of liberty for ourselves and future generations.