This book analyses the changes of welfare states, examining their sustainability enabled by innovative adaptations. On the basis of evolutionary social sciences, the authors understand the welfare states as complex adaptive systems, in which the actors' perceptions, strategies and behaviours change in adaptive manners, which results in institutional changes. From this perspective, the dynamics of Nordic welfare states, mainly Finland as the Nordic welfare state under the greatest pressure to adapt, is analysed from the multiple perspectives of history, politics, economics and social policy. Through these analyses, the authors show that the long-term changes in welfare states can be creative evolutionary processes in which the experiences, cognitive frameworks, resources and capacities of different actors allow for diverse responses and, as a result of interaction, diverse outcomes. The book also illustrates the historical processes of welfare states' formation that have created the human and social resources and capabilities that enable innovative responses today.