Philus (The Defense of Injustice, Cicero _online_) begins his argument by saying he will use the techniques of Carneades, who proposed an argument against justice. Carneades was a skeptic philosopher famous for arguing against many worthy positions and beliefs. He made a point of undermining positions that were thought to be obvious and secure--such as the position that supports justice as a positive virtue. Try this method (after reading the essay) by arguing against an obviously desirable position.