The Founding Fathers, and others who did input ideas and helped debate options and such thoughts prior to our Country's birth, thought it would be useful and more meaningful to do our government bassackwards, that is we reserve all authority in the People, and some is delegated to the States, and lastly some limited authority is delegated to the Federal government.

To ensure God's Laws and Human Rights were protected a Bill of Rights - the Amendments - was appended immediately to the broad outline of the Constitution. The Constitution itself is short and sweet, delineates the purpose of government, defines our Man's Laws as codified from God's Laws really.

But to keep those Rights safe we must enumerate them - so the Bill of Rights is appended, listing Religion and Speech and arms and other inalienable Rights. In that fashion the Rights granted to us all by God are codified into our government's very being. It is why we are unique, our Bill of Rights is 'that mechanism' which protects our Law, our Freedom from a tyrannical government. All democratic republics historically fall to corruptions from within - the Amendments were originally designed to prevent that by mandating an Armed Citizenry which holds the vast majority of Power and Authority.

In that sense our Constitution is a living document; it carries within itself it's own mechanism for appending certain Societal desires into Law and also carries the means of it's own defense.

Read The Federalist Papers sometime, fascinating stuff, watching such momentous ideas fabricate themselves through the papers floating back and forth is tremendous History.