This chapter explains the concept of reliance and reliance systems – the way in which human agency stems from collectively produced systems. It then links this understanding of reliance and agency to capabilities theory, and explains the contribution that reliance systems make to rendering capabilities theory more aware of the materiality of capabilities. The chapter then delves into the nature of reliance systems, focusing on separating the material and functional components of reliance systems. We explain the need to modify social contract theory in order to pursue a better politics of reliance systems, as opposed to other possible political avenues such as rights and deliberative democracy. The chapter ends by suggesting six principles for examining the morality of any given spatial contract.

The introduction lays out the basic intellectual framework of the book. It argues that human agency is derived from collectively produced reliance systems such as energy, transportation and water. These systems are governed by complex formal and informal agreements called spatial contracts, which differ depending on the system, geography and moment in history. These spatial contracts need to become the focal point of twenty-first-century politics.

This chapter focuses on building an analytical framework for understanding reliance systems and spatial contracts. It is based on the argument that we must begin with the system, and understand the politics from the system up, rather than from the politics down. The framework draws on systems thinking to establish how we can differentiate between different systems. It then uses this systems perspective to repurpose ideas from economics which are useful if focused on systems instead of commodities.

This chapter furthers the development of the analytical framework by focusing on the relationship between reliance systems and exploitation. It reworks Iris Marion Young’s five faces of oppression for use with reliance systems and the spatial contract. These five faces are exploitation, marginalization, powerlessness, cultural imperialism and violence.

This chapter continues the work of building the analytical framework. Rather than pulling apart systems to appreciate their differences, as in Chapter 2, this chapter explains how systems must be seen together as human settlements. This settlements perspective illuminates two important sets of divisions that may hinder the development of healthier spatial contracts – the divide between urban and rural, and that between formal and informal.

This chapter summarizes the key contributions of the book. It highlights the way the text operates as three interlocking frameworks: an intellectual framework focused on an understanding of the relationship between collectively produced systems and human agency; a political framework which insists on the need for these systems to become the centre of politics; and an analytical framework which understands systems in context, with a focus on exploitation. It further demonstrates the utility of these frameworks by briefly analysing two current cases: the push for universal basic income globally, and the focus on the Green New Deal in the United States. The chapter also lists ten areas where future work is needed.

Intermediary actors are key catalysts in accelerating sustainability transitions. Since 2019, the academic literature on intermediaries and intermediation has expanded rapidly, leading to inconsistent usage, proliferating lists of activities, and questions about their impact on transition processes. These challenges risk making the concept fuzzy and less accessible while limiting its practical relevance. This chapter provides an accessible introduction to intermediaries in sustainability transitions, followed by a historical account of the concept’s development. It then presents empirical examples of intermediaries and their activities, highlighting a key gap: the lack of an explicit theory on why intermediaries exist in transition processes. To address this, we position intermediaries alongside other actors, such as system entanglers, orchestrators, and champions. This chapter concludes by outlining future research directions, emphasizing the need to move beyond individual intermediaries to ecologies of intermediation as transitions accelerate and interact.

Chapter 2 establishes the fundamentals of sustainability, building from the Brundtland Report’s definition of sustainable development through contemporary frameworks like planetary boundaries and doughnut economics. It introduces the Earth-as-endowment metaphor to illustrate humanity’s relationship with planetary resources and explores the Nordic region’s significant contributions to sustainability thinking and practice. The chapter examines how overconsumption threatens Earth’s regenerative capacity and details Nordic innovations in environmental protection, circular economy, and climate policy. It concludes by addressing the challenge of overcoming sustainability denial, particularly in the United States, while highlighting the Nordic region’s pragmatic approach to environmental challenges. Throughout, the chapter emphasizes systems thinking and the interconnected nature of sustainability challenges, establishing theoretical foundations for examining capitalism’s role in advancing sustainable development.

In the final chapter of this handbook, we reflect on the development of sustainability transitions research (STR) by examining its origins, core focus, achievements, critiques, and future directions. Using the metaphor of a tree, we argue that STR has grown from deep roots in various disciplines to develop a broad crown of research branches, all connected by a shared focus on socio-technical change. The field’s rapid expansion brings both opportunities and challenges. While a common language fosters interdisciplinary collaboration, it also risks rigidity and exclusivity, highlighting a tension between cohesion and fragmentation. Additionally, disseminating STR findings into its foundational disciplines and addressing growing political and social responsibilities remain key challenges. STR forms a robust community while requiring ongoing (self-)reflection. Rather than defining its trajectory, we aim to foster dialogue on STR’s evolution, recognizing that, like a tree, research fields need continuous nurturing to remain vital and productive.