Every year, I renew my subscription to American History and every year they send me a small, softbound book with the Declaration of Independence and the Constitution with Amendments in it. This year, I decided to read it, starting with the introduction and commentary. It explains some of the thinking the Founders had, some of their motivations.
From the book:
Thus, the cardinal moral truths are these:
... that all Men are created equal, that they are endowed by the Creator with certain unalienable Rights, that among these are Life, Liberty and the Pursuit of Happiness -- That to secure these Rights, Governments are instituted among Men, deriving their just Powers from the Consent of the Governed.