In virtually all decision processes in these complicated systems, there are various actors (decision makers) who represent individual subjects (persons, countries, companies, etc.) and their respective interest groups. This makes the decision making process difficult as one cannot employ conventional "hard" tools.

1. Introductory Sections.- Consensus, negotiation and mediation.- Fuzziness and the normative theory of social choice.- Types and measures of uncertainty.- 2. Tools and Techniques for Measuring and Monitoring Consensus Reaching.- “Soft” degrees of consensus under fuzzy preferences and fuzzy majorities.- An approach to the consensus reaching support in fuzzy environment.- The dichotomous approach to soft consensus measurement.- Consensus based on fuzzy coincidence for group decision making in linguistic setting.- Modeling preference relations and consensus in a linguistic environment: an approach based on OWA operators.- 3. New Paradigms and Architectures for Modeling Consensus Reaching.- Protocol for negotiations among multiple intelligent agents.- The development of fuzzy consensus via neural modelling.- 4. Auxiliary Formal Tools and Techniques for Modeling Consensus Reaching.- Consensus for decomposable measures.- Construction of fuzzy utility functions in group decision making.- Problem solving with multiple interdependent criteria.- Lexicographical solutions in n-person cooperative games with multiple scenarios.- 5. Applications and Case Studies.- Identification of ideological dimensions under fuzziness: the case of Poland.- Determining weights of research topics on the basis of expert judgments. The case of Systems Research Institute.