The dissertation analyses the capacity of contractualism and natural law to justify environmental intergenerational duties. For three decades, climate change has been a major political concern. As a fundamental threat to environmental sustainability, climate change is believed to threaten the long-term welfare of humankind. It thus seems imperative to affirm long-term duties regarding future people’s environment. Furthermore, contractualism and natural law are two important moral theories in contemporary political life. While the former seems influential among political liberals, natural law seems more appealing to political conservatives. It is thus of interest how both of these theories can be used to argue for environmental intergenerati...