In the following, an attempt is made to summarize the various aspects discussed in this book, and synthesize the ideas, perceptions and visions brought forward by the authors and discussed in the working groups and the plenary session. "Sustainability" certainly contributes to the sensibility of our society towards the responsibility for the future of mankind. However, the conception of sustainability discussed so far does not have a clear target. We experience a diffusion of the definition. Thus, sustainability is used by the various groups of interest just as they need it. A prerequisite is a substantiation of the conception with the effect that it can be utilized as an instrument for the diagnosis as well as for the necessary actions to be taken. The postulates that will result from this condensation exercise may pave the way towards a greater understanding of the interrelationships between the economic, social, ecological and cultural dimension of sustainability. They may provide a viable basis for further research and investigation, and a guideline for decision makers in science, industry and State governments.