Introduction cant changes in the Senate over the last two decades,tend- ing toward more decentralization,more openness,and more equal distribution of power,have come without abat- ing the folkway of reciprocity (Ornstein,Peabody,and Rhode 1977).As will be seen,it is not necessary to assume that senators are more honest,more generous,or more public-spirited than in earlier years to explain how cooper- ation based on reciprocity has emerged or proved stable. The emergence of cooperation can be explained as a conse- quence of individual senators pursuing their own interests. The approach of this book is to investigate how individ- uals pursuing their own interests will act,followed by an analysis of what effects this will have for the system as a whole.Put another way,the approach is to make some assumptions about individual motives and then deduce con- sequences for the behavior of the entire system (Schelling 1978).The case of the U.S.Senate is a good example,but the same style of reasoning can be applied to other settings. The object of this enterprise is to develop a theory of cooperation that can be used to discover what is necessary for cooperation to emerge.By understanding the condi- tions that allow it to emerge,appropriate actions can be taken to foster the development of cooperation in a specific setting. The Cooperation Theory that is presented in this book is based upon an investigation of individuals who pursue their own self-interest without the aid of a central authority to force them to cooperate with each other.The reason for assuming self-interest is that it allows an examination of the difficult case in which cooperation is not completely based upon a concern for others or upon the welfare of the group as a whole.It must,however,be stressed that this assumption is actually much less restrictive than it appears. 6Introduction cant changes in the Senate over the last two decades, tend￾ing toward more decentralization, more openness, and more equal distribution of power, have come without abat￾ing the folkway of reciprocity (Ornstein, Peabody, and Rhode 1977). As will be seen, it is not necessary to assume that senators are more honest, more generous, or more public-spirited than in earlier years to explain how cooper￾ation based on reciprocity has emerged or proved stable. The emergence of cooperation can be explained as a conse￾quence of individual senators pursuing their own interests. The approach of this book is to investigate how individ￾uals pursuing their own interests will act, followed by an analysis of what effects this will have for the system as a whole. Put another way, the approach is to make some assumptions about individual motives and then deduce con￾sequences for the behavior of the entire system (Schelling 1978). The case of the U.S. Senate is a good example, but the same style of reasoning can be applied to other settings. The object of this enterprise is to develop a theory of cooperation that can be used to discover what is necessary for cooperation to emerge. By understanding the condi￾tions that allow it to emerge, appropriate actions can be taken to foster the development of cooperation in a specific setting. The Cooperation Theory that is presented in this book is based upon an investigation of individuals who pursue their own self-interest without the aid of a central authority to force them to cooperate with each other. The reason for assuming self-interest is that it allows an examination of the difficult case in which cooperation is not completely based upon a concern for others or upon the welfare of the group as a whole. It must, however, be stressed that this assumption is actually much less restrictive than it appears. 6