It's quite obvious what Jefferson means in this quote. When he wrote the Declaration of Independence, he clearly stated, ..."That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, — That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness." This excerpt states that: 1) Government exists because the People gave it the power to exist; 2) When the Government fails to do its job, or, in this specific case, breaks away from the control of the People, it should be changed or abolished. 3) It is the right of the governed to do this. Jefferson's quote goes on to further this by saying that it is essentially the right and duty of the governed to keep their government in check, even if it means bloodshed. I'll end this with another relevant quote, "They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety." -Benjamin Franklin