In his book, Jack Donnelly argues for a revival of systems-based theory in international relations (IR), drawing inspiration from evolutionary biology. He asserts that a true systemic theory must integrate the analysis of individual components (e.g., structure or units) with an understanding of organized, structured wholes. Donnelly believes that the structural framework proposed by Kenneth Waltz was not a systemic theory and that it actually hindered scholars from developing systemic approaches, thereby obscuring our understanding of international systems. In this book, Donnelly proposes an alternative relational and systemic approach to IR.

Donnelly builds on his earlier work on differentiation, hierarchies, and realism, structuring the book as a comprehensive plea for multidimensionality and plurality in IR. The text is flexibly designed, allowing chapters to be read independently and in any order, although newcomers to Donnelly's work should start from the beginning. The initial section methodically presents the core arguments, positing that the social world—like the biological one—can only be fully grasped through a mix of analytical and systemic knowledge (3). Donnelly invites researchers to engage in systemic and relational research and explanation, focusing on the organization and operation of the whole system rather than just on the str