The concept of sustainability explained in Chapter 2 is further developed in terms of human capabilities proposed by Amartya Sen and Martha Nussbaum. Human capabilities are defined as “real freedoms that people have reasons to value.” Some of these capabilities may be quite elementary, such as being adequately nourished and escaping premature mortality, while others are more complex, such as having the literacy required to participate actively in political life. In contrast to utility-based and resource-based approaches (that is, utilitarianism and Rawls’s theory of justice, respectively), human capabilities provide a robust informational basis for interpersonal comparisons that is necessary to reduce injustices and advance good societies. They are relevant for all types of capital (natural, economic, human and social) as well as for private and public goods and wealth.