Individual decisions have to be aggregated to make group decisions. Markets aggregate decisions by consumers and producers into prices that might reflect social values. But markets allow and generate inequalities, and many aspects of human well-being and the environment do not have market prices. In large societies, direct voting on some policies is possible but most voting is for representatives who become part of a larger policy system. Deliberation is an ideal that underpins most justifications for democracy. It can be linked effectively to scientific assessments at the local to regional level. Ways to use deliberation at the national or global scales require further experimentation. In the United States, high levels of polarization challenge the idea of public deliberation. New technologies will create further challenges for sustainability decisions. Identifying strategies to move forward requires understanding variation in the public and drawing on strategies for nonviolent social change and conflict resolution.

Making good decisions about sustainability requires explicit consideration about what criteria to use. Three grand traditions dominate most policy discussions: utilitarianism, deliberative ethics and anarchism/libertarianism. The chapter proposes seven criteria for good decisions. Three are criteria for the outcomes. A good decision should enhance the well-being of humans and other species while reducing stress on the environment; be efficient in allocating resources; and enhance individual freedoms. Four are criteria about process: take account of uncertainty in both facts and values, as well as value conflicts; promote fairness in both the decision process and its outcomes; rely on human cognitive strengths and compensate for weaknesses; and allow for social learning.

After the Great Depression and World War II, a compromise between industry and labor made economic growth a priority, with the assumption that growth would reduce inequality. The ideal of democracy inspired liberation movements across the globe and was invoked to justify most governments. Concerns with biodiversity and with environmental risks to human health were merged in the modern environmental movement. The idea of sustainable development incorporated environmental concerns into the push for economic growth. Uncertainty in scientific analysis was codified in the concept of risk, and risk analysis became an important form of policy analysis. Neoliberal policies promoted unfettered markets to promote growth. But growing concerns with the impacts of population and economic growth led to a call for sustainable development, with the twin goals of improving human well-being and reducing stress on the environment. The United Nations Sustainable Development Goals articulate this idea and demonstrate its complexity.

Three theoretical traditions dominate our understanding of decision-making. The rational actor model assumes individuals are self-interested and maximize their utility subject to budget and time constraints. When outcomes depend on the decisions of others, as in the problem of common pool resources, trust and norms can avoid support sustainability. Social psychological models examine the role of values, especially altruism and self-interest, beliefs, norms, identity, emotions, empathy and trust in decision-making. The heuristics and biases literature shows that decisions are often based on mental shortcuts that deviate from the rational actor model. Our tendency towards biased uptake of new information and communicating mostly with those similar to us can lead to polarization. The three theories can be viewed as complementary: each yields important insights into decision-making.

Climate change and other global processes shape and are shaped by local process such as land use change. Does the idea of sustainability help us take account of both human well-being and the environment at the local and global level? To answer, we have to unpack what is involved in decision-making and what sustainability means. Decisions are made in multiple roles: consumer, citizen, role model for others, organizational participant, investor, and resource manager. In all of these roles, context, including inequalities, shapes opportunities and constraints and thus decisions. Context often reflects a long history of previous decisions, including discrimination. Thus context and choice are two views of the same process.

Corporations make decisions that are crucial for sustainability. Can corporations, by taking account not just of profits but of impacts on people and the environment, support sustainability through ongoing reforms? Or does sustainability require a transformation of the global political economy? An evolutionary perspective focuses attention on variation across corporations and the selective pressures that shape their actions. Partial solutions can cumulate to substantial change and buy time for further change. But spillover effects where one action either facilitates or retards another can slow or speed change and seem to vary across the types of action considered. Proposals for change need to take account of not only what would happen if the change occurred but also the likelihood the change will occur.

Multiple strategies can be used to influence individual decisions. A common assumption is that a lack of information, an information deficit, leads to poor decisions. While that is sometimes true, since decisions are shaped by both facts and values, providing information is often insufficient to change decision-making. The rational actor model suggests that changing incentives, and in particular changing prices, will shift decisions. Incentives matter, but they are only one factor in decisions and shifting incentives can be inequitable. Values are difficult to change but have broad and long-lasting influence on decisions. Norms are relatively easy to change and can have substantial influence. Design principles, generalizations from research on decision-making, can help shape effective efforts to influence decisions. Policies and programs should be designed with the consent of and in collaboration with those who may be impacted by the decision.

Conflicts around sustainability decisions are driven by at least eight forces. The distribution of risks and benefits is uneven, creating winners and losers. Facts and values, while logically distinct, are often confused. Facts are uncertain. The value implications of emerging issues are not clear. Decisions bring about permanent, concrete changes making compromise difficult. Those disadvantaged by a decision often have little say in it and did not generate the problem, raising concerns about harm to innocents. The boundaries between what is public and what is private are often confused and contested. Competence about some aspects of decision-making, such as assessing facts, can be confused with competence about other aspects of decision-making, such as assessing values. In addition, major long-standing controversies about transforming political economies and ecosystems are part of the background to most sustainability decisions.

In decision-making, facts should be distinguished from values. Values influence the decisions by scientists about what kinds of research to do and how to do it. But the norms of science, over time, promote the evolution of increasingly accurate understanding of facts. It is easier to establish facts when observations are repeatable and ostensible. Sustainability decisions usually require assessment of facts in very specific contexts, and that can increase uncertainty. In such cases, deliberation with interested and affected parties can help get the science right and get the right science. When the powerful see their interests threatened by increasing awareness of risks, they often try to slow the emergence of scientific consensus, especially by emphasizing uncertainty.