Paul sums up his argument of everyone being guilty of falling short of God's righteousness by referencing Scripture - the best defence. Near the end of this passage, it's concluded that every mouth will be stopped. In other words, no one can have a defence when it comes to living up to God's standard. When our Creator asks, "How do you plead?". Everyone has to respond, "Guilty, your Honour!" This is the first step in coming to faith in Christ.