This is a quote from a 1987 book, specifically from a lecture given by one Joseph Cardinal Ratzinger - now Pope Benedict XVI. The full text is on LewRockwell.com.
"Where conscience prevails there is a barrier against the domination of human orders and human whim, something sacred that must remain inviolable and that in an ultimate sovereignty evades control not only by oneself but by every external agency. Only the absoluteness of conscience is the complete antithesis to tyranny; only the recognition of its inviolability protects human beings from each other and from themselves; only its rule guarantees freedom."
These are certainly words to live by. One does not have to be Catholic to agree.