This principle is a direct consequence of reflecting the external reality based on image models. The evolution of society means that there is a dynamic (a continuous change in time). But, as we already know, it is very hard to change a structure of models. A second principle states that: The persons who are able to lead the society must be changed from time to time, even if they seem to be able to lead the evolution process. The first principle says that a team of "symbolic" qualified persons should elect the leading persons, and the second principle says that such persons must be changed from time to time. The present democratic society is based on these principles, as MDT just explained why. When in a situation associated with the evolution of the society, a decision has to be taken; on image models, the decision is based on feelings, or impressions, or some local models. On a symbolic model, such a decision is based on parameters and their associated values. So, the importance of every element or relationship is controllable. Example: there is a law of the propagation of errors in mathematics. It says how much the result of a formula is changed when a term is changed, let's say, e.g. by 1%. The importance of every element or relationship is given in a very precise way. In future (not in the next 50 years, I guess), there will be a single symbolic model associated to the society. Such a model will be able to characterize the society in the same way as the mechanical world is characterized by Newton's model. Based on simulation, it will be possible to predict the evolution of the society, based on some basic decision. The population will have to know these predictions and choose one or another based on its short-range and long-range interest. It is supposed that in some very advanced countries such models already exist. The main problem is that the political parties and the population are on a general evolution level that is too low for a "symbolic" understanding of the society. ETA 19: The schizophrenic-paranoiac complex (XSPC). XSPC is described only associated to non-pathological schizophrenic persons (XS1-type). Based on MDT, schizophrenia means a reduced ability to build and operate long- range models. XS1 schizophrenia is a non-pathological form, which is associated with the activity of a large fraction of the population in a normal society. Paranoia XP means that there is an ordinary model in the protection structure of models. Such an OMPSM forces a person to distort the importance of the primary facts to be accepted by OMPSM. Thus, an XS1-type person is not able to build long-range models, but he/she is able to build short-range models. The result is that such a person has a large number of short-range models, which are associated with almost all the features of the external reality. A XS1 person is able to integrate into a society, often in very good positions.