"The Declaration is speaking of the overall purpose of government. The Preamble to the Constitution, in contrast, is speaking only of the reasons for adopting this Constitution. The purpose of a particular constitution is a lesser question than the purpose of government. A nation can have a government without having a constitution. It would not be wise, of course; but it can be done."
"Specifically the Preamble to our Constitution mentions six reasons for supporting the Constitution. Those six reasons are:"
"[1.] form a more perfect Union,
[2.] establish Justice,
[3.] insure domestic Tranquility,
[4.] provide for the common defense,
[5.] promote the general Welfare, and
[6.] secure the Blessings of Liberty to ourselves and our Posterity."
"It is obvious from this list that the reasons given are those in favor of adopting this Constitution as opposed to a continuation of the Articles of Confederation. The preamble does not presume to be a statement of the overall purpose of government. It should also be observed that if the Preamble to the Constitution actually did elevate the common good to the same level as protection of the unalienable rights, then it also elevates national defense and the other goals to the same level. No one seems to want to make that case, however, further illustrating the error in the position of the national standards."