Through this exercise, students would continue their practice of confirmation and refutation that had already begun in earlier exercises.
According to Theon, one may refute laws according to the following topoi: what is "unclear, impossible, unnecessary, contradictory, unjust, unworthy, inexpedient, shameful." (Theon 129, Kennedy). According to Hermogenes, the topics by which to refute or confirm a law are: "clarity, justice, legality, advantage, possibility, appropriateness." (Hermogenes 27, Kennedy).
In Mark 10 there is a discussion of the law concerning divorce. The setup is as follows:
Some Pharisees came, and to test him they asked, “Is it lawful for a man to divorce his wife?” He answered them, “What did Moses command you?” They said, “Moses allowed a man to write a certificate of dismissal and to divorce her.” (Mark 10:2-4).Now, in what follows, Jesus will refute this law of writing a certificate of divorce, and he will do so using a number of the topics listed above. Jesus responds thus:
But Jesus said to them, “Because of your hardness of heart he wrote this commandment for you. But from the beginning of creation, ‘God made them male and female.’ ‘For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh.’ So they are no longer two, but one flesh. Therefore what God has joined together, let no one separate.” (Mark 10:5-9).It was because hardness of heart that Moses wrote this provision of the law, but that does not conform to the Law of God. Therefore, Jesus refutes this provision of the Law based on several different fronts. It could be seen as truly "illegal" based upon God's law. It could be seen as "shameful" based upon the shame of having a hard heart. It could be seen as "inappropriate" based upon its failure to conform with the perfect plan of God.
Practice in confirmation and refutation of laws was of great importance for the biblical writers, and the progymnasmata would have instructed Greek students in performing such tasks.