For thousands of years the concept of justice has been widely discussed in philosophy jurisprudence and political economics.

The best known theory of justice in our time is John Rawls' concept of "Justice as Fairness". This is an attempt to develop principles of behavior using the fundamental assumption of a "veil of ignorance" thus ensuring that those developing the principles are unaware of the effect of the results on their own lives.

Rawls believed that this approach yielded rules that were fair to all citizens, independent of their social situation.

Justice, however, becomes a problem only when such rules are violated and the more frequently such violations occur, the greater the problems concerning a nation's justice and stability.

Rawls does not tell us what the authorities should do once their citizens begin to break the rules. This is an awkward gap since we know from experience that societies without such violations have never existed.

What we need therefore, is an empirically founded theory of justice which respects facts.

The theory proposed here incorporates justice and solidarity as dynamic variables which are subject to statistical measurement. Our theory, like all the others, is based on binding rules governing behavior. These rules are identified through experience and are applicable globally. We refer to these rules as "duties". Two well known examples of the duties, identifiable through common sense, are to help someone in need or to work. Another example is to refrain from violence. The first examples are active, the second example passive.

The current situation of any nation can be described with the help of sets of passive duties constructed using computer based simulation.

A single set can be represented as a behavior vector b with n components b(i). The larger the natural number n the greater the precision of the resulting profile.

The duties are designed to get agents to refrain from acts that jeopardize global stability. The components of a behavior vector must be mutually compatible to ensure the possibility of their simultaneous compliance by as many agents as possible.

Apparent collisions among non elementary duties are often the result of our incomplete scientific knowledge. An example of such a collision is the contradiction between the need for clean energy and the prohibition of combustion power plants.

Each of the components of a behavior vector b contributes to reduce a specific global system risk r(i). In some respect a behavior vector b and as well the attached risk vector r both reflect the state of technological, economic, and scientific development of today's global civilization.

The components of r are probabilities with values between zero and one. A single passive duty b(i) reduces a respective global system risk r(i) by refraining from the act prohibited by b(i). If an agent knows the passive duties, the agent is able to respect them.

If the totality of risks r(i) of r equals zero, nations would contribute their maximum to avoid global self-destruction. Furthermore no human being worldwide would suffer from made-made harm. This maximal situation - which we call the ideal risk state - is never reached in reality. The smaller the risks r(i) of r, the better the nation's contribution to global stability and the better for individual life chances in the respective nation. To minimize individual harm and to maximize total stability, national solidarity must statistically be as high as possible. This means that as many agents as possible must be well educated and the national economy must be competitive worldwide. Otherwise too many individuals must struggle to survive and are therefore forced to neglect passive duties to be able to help themselves and their families.

If all components of the behavior vector b are universally obeyed, the rules b(i) , taken together, are win-win-rules for each individual, the respective nation and all its social subsystems. This situation actually occurs only with small social subsystems. However, the more individuals globally - as well nationally - follow the win-win-rules the more stable the world civilization and - as well the internal national stability.

Not all agents of a nation belonging to the same global civilization are liable to violate all passive duties of the behavior vector: If e.g. a nation has no rain forest on its territory, then the passive duty to refrain from clearing the rain forest is not "switched" in the respective behavior vector describing the nation; this means that the respective component of the nation's behavior state vector b has the value zero.

The smaller the actual risk components r(i) of r describing a nation's risk state vector the higher the actual value of solidarity. Due to strong correlations between active and passive duties low risks r(i) reflect the fact that statistically it is not necessary to violate passive duties to survive. The ideal value for solidarity would belong to a risk state vector r of a nation, where all r(i) would equal zero. This ideal value never can be reached in reality.

Collective solidarity should not be confused with the wide-spread political concept 'social justice'. If these two words have any meaning at all they characterize a nation of more equality. But greater equality collides with the possibility to assist weaker individuals effectively and hence reduces the nation's actual collective solidarity.

As already mentioned, the justice of nations becomes a problem if agents violate components of b which vary from zero. The more agents are forced by their individual critical social situations to violate these rules the more the nation's collective justice is endangered. The reason for this is easy to understand: If a first agent must struggle to survive because nobody in his nation is able to assist because of severe gaps in the agents' education, this struggling agent can survive only by violating some of the rules incorporated in b. Hence a high collective solidarity is the best antidote for the increase of a nation's injustice.

As already mentioned behavior vectors are to be constructed by computer simulation. In a first step many possible passive duties are identified. Only the duties b(i) with strongest mutual correlations finally describe the final dynamic state vector f describing best the global civilization. If simultaneously obeyed the components of f minimize harm and maximize stability in a linear fashion.

Due to strong correlations among the components of the global behavior state vector f, it might in many cases be sufficient to measure regularly the so-called social temperature T: T is higher the higher the risks pertaining to passive duties prohibiting any kind of violence including violence of state authorities against citizens. Imprisonment as a result of legal transgressions is a key aspect of state violence. The higher the value of T, the more unstable the nation and the more citizens suffer from human-induced harm. Therefore a higher T is an alarm signal and a lower T a sign of greater interior tranquility.

As soon as citizens or state authorities violate passive duties harming human beings, only interventions are able to limit the harm that has been done. Agents or nations, who are in the position due to their power, competence and expertise to intervene in a conflict among citizens or citizens and state authorities heavy violating global rules of behavior, have to intervene in order to limit the harm arising from the primary contravention of passive duties. The internal intervention is successful, if additional harm - including imprisoning by state authorities - through the intervention is small compared with the original harm. The value of the nation's total harm after all contraventions of components f(i), which do not equal zero, and all interventions measures the actual value of justice in the respective nation. This value may change from year to year as can the value of T.

If an intervention - preferably by state authorities - is neither promptly nor successfully carried out, then the first violation of a passive duty can be compared to an infection which may spread throughout the nation and raise the overall risk of self-destruction.

This empirical approach to a "Theory of Solidarity and Justice" can serve to diagnose a nation`s current situation and its foreseeable evolution in the nearer future. It cannot, however, solve political problems in detail, concerning the nature of successful interventions for strengthening interior or exterior peace and as well "peace of nature" (Meyer-Abich). Peace of nature means in the end a global economic system with zero waste and zero emission.