In private international law, the public policy doctrine or (French: "public order") concerns the body of principles that underpin the operation of legal systems in each state. This addresses the social, moral and economic values that tie a society together: values that vary in different cultures and change over time. Law regulates behaviour either to reinforce existing social expectations or to encourage constructive change, and laws are most likely to be effective when they are consistent with the most generally accepted societal norms and reflect the collective morality of the society. In performing this function, Cappalli has suggested that the critical values of any legal system include impartiality, neutrality, certainty, equality, openness, flexibility, and growth. This assumes that a state's courts function as dispute resolution systems, which avoid the violence that often otherwise accompanies private resolution of disputes. That is, citizens have to be encouraged to use the court system to resolve their disputes. The more certain and predictable the outcome of a court action, the less incentive there is to go to court where a loss is probable. But certainty must be subject to the needs of individual justice, hence the development of equity. A judge should always consider the underlying policies to determine whether a rule should be applied to a specific factual dispute. If laws are applied too strictly and mechanically, the law cannot keep pace with social innovation. Similarly, if there is an entirely new situation, a return to the policies forming the basic assumptions underpinning potentially relevant rules of law identifies the best guidelines for resolving the immediate dispute. Over time, these policies evolve, becoming more clearly defined and more deeply embedded in the legal system. Fundamental principles Ignorance of the law is not an excuse The fundamental policy in the operation of a legal system is that ignorantia juris non excusat (ignorance of the law is no excuse). It would completely undermine the enforcement of any law if the person potentially at fault was able to raise as a successful defence that he or she had not been aware of the particular law. For this reason, all the main legislatures publish their laws freely whether in hard copy or on the Internet, while others offer them for sale to the public at affordable prices. Because everyone is entitled to access the laws as they affect their personal lives, all adults are assumed responsible enough