Antiphon is bracing the question of relativism (at a cultural level): ” … by nature we are all at birth in all respects equally capable of being both barbarians [i.e foreigners] and Greeks.” (Annas, p375) There are attributes held by all men regardless of origin or location. For instance, to breathe, laugh when pleased in mind, cry when pained and take in sounds through hearing in the ears. Justice is not part of these natural attributes. Justice is not violating the rules of the city in which one is a citizen. Therefore the requirements of justice are supplementary, and the requirements of nature necessary. The requirements of the laws are by agreement and not natural, and the requirements of nature are natural and not agreed. Justice then hinges on witnesses; the presence of other citizens. One can avoid shame if the law broken goes unnoticed by others. Laws apply to the actions of people; what they should and should not do, say, see, hear. The advantages laid down by laws are a bond on nature, but those laid down by nature are free.
Antiphon seems to be developing a criticism on the law in which he points out that virtuous behaviour receives little assistance. The law allows the victim to suffer and the agent to act. In the court, the victim has a burden of proof, to which the agent has an equal opportunity to deny. A new argument emerges in context of the court room situation in which he who testifies is acting to injure the person to whom he testifies against (whether guilty or not does not matter in this particular exchange). He is injuring someone who did not injure him. This is construed as an otherwise avoidable creation of enemies: the defendant and the witness. It is inconsistent to say that the rule to not injure someone else is just, if the justice system requires one person to hurt another in its proceedings.
The logic here is clear, though somewhat removed or naive of the reality of complex human relationships. To follow this logic would lead to a stasis in which any sense of justice would collapse all together. If no one can injure anyone else in the context of the courtroom, the ability of the society to observe and learn from its citizenry would be at a standstill. Injuries that take place in the world, whether deliberate (theft, murder) or accidental (property damage, unforeseen consequences of some development or other) will never be resolved or compensated. The logic put forward by Antiphon is not sound as it is not true. It lacks detail on the level of nuanced case by case examples. One question might be to what extent can it be considered virtuous to seek the truth in the courtroom in order to resolve a case, and might this virtue outweigh the injury perpetrated by a witness against a defendant. Might injuries in general have different classifications? For instance, murder might be a more grievous injury than a damning testimony by a witness, in which case it is justified for the witness to cause injury to the defendant in order to resolve the murder.