 Cicero’s thinking seems to be that to regard laws as no more than human artefacts – that is, as not based in nature – is to concede that reward and punishment are the only motivations for obedience. But then it will be the rewards and punishments, not the justice or injustice of the act in question, that will have normative force. But if that is so, then if one calculates correctly that, say, greater utility will arise from breaking than obeying a law, it seems that one has no reason to obey it. What is needed, rather, is a conception of justice as something to be sought, as Cicero puts it, ‘for its own sake’ (1.48). That is, we must think of what is just as having an inherent normative force, to be pursued because it is just. And that means, for Cicero, that justice must be based in nature and not simply a matter of human convention.