(a) The design of the legislative branch of the US government, the Congress, is described in Article I. The division of powers between departments of government (checks and balances), the election of Senators and Representatives, the legislative process, and the authority of Congress are all important concepts.
(b) "If there is any principle of the Constitution that more imperatively calls for attachment than any other it is the principle of free thought, not free thought for those who agree with us but freedom for the thought that we hate." - Oliver Wendell Holmes, Jr.
(c) "The basis of free thinking is not free thought for those who agree with us, but freedom for the thought we despise," writes Supreme Court Justice Oliver Wendell Holmes in 1929. That is, we must allow everyone, not just those who agree with us, to speak freely.