Quotes from Greg Bahnsen

The civil magistrate cannot function without some ethical guidance, without some standard of good and evil. If that standard is not to be the revealed law of God… then what will it be? In some form or expression it will have to be the law of man (or men) - the standard of self-law or autonomy. And when autonomous laws come to govern a commonwealth, the sword is certainly wielded in vain, for it represents simply the brute force of some men's will against the will of other men.

When revealed theology is reduced to an autonomous study of man, when biblical authority is replaced by an unstable human wisdom, when behavior is directed by the descriptions of social science instead of the prescriptions of God's Word, then we have returned to the situation prevailing at the time of the Book of Judges: every man will do what is right in his own eyes.