The topic of my thesis is individual and collective responsibility for collectively caused systemic harms, with climate change as the case study. Can an individual be responsible for these harms, and if so, how? Furthermore, what does it mean to say that a collective is responsible? A related question, and the second main theme, is how ignorance and knowledge affect our responsibility. -/- My aim is to show that despite the various complexities involved, an individual can have responsibility to address (...) climate change. I argue that climate change is not a problem just for states and international bodies, but also for individuals. There are three possible sources of moral responsibility for individuals in relation to climate change harms: direct responsibility (individuals qua individuals), shared responsibility as members (individuals qua members of collective agents), and shared responsibility as constituents (individuals qua constituents of unorganised collectives). -/- Accounts that deny individual responsibility fail to either take our interdependent reality seriously or fail to understand marginal participation (or in the case direct responsibility, fail to appreciate the nature of the climate change phenomenon). Individuals can be complicit in climate change harms, either as members of collective agents (e.g. as citizens of states or employees of a corporation) or as constituents of unorganised collectives (e.g. as consumers or polluters). -/- Although I focus on individual complicity, I do not deny the obligations of collective agents. However, nation-states, governments, and international bodies are not the only relevant collective agents in climate ethics: other collective agents, such as corporations, matter also and can have obligations concerning making sure that their activities are as carbon-neutral as possible. In addition, those corporations that have engaged in lobbying against climate regulation through creating and disseminating misleading information have acquired themselves additional obligations to mitigate climate change and compensate for the harm they have caused. Even so, the ethical claims can only be understood by individual members of these collective agents because only they can feel the pull of moral claims. I suggest that we could distinguish between what one must possess in order to be capable of making moral claims (i.e. moral agency conditions), and what it means to have the ability to exhibit such claims through one’s conduct. -/- Individual direct responsibility is to not to increase the probable risk of serious harm to other people, at least as long as we can do so at a less than significant cost to ourselves. It is limited to relatively wealthy individuals. Offsetting is not a reliable way to meet this duty; we need to look at the emissions from our lifestyle choices (within the available infrastructure). Shared responsibility qua members of collective agents is the key individual responsibility, and it presses especially on those occupying key positions within key collective agents. Saying that, our shared responsibility qua constituents of unorganised collectives has the potential to be decisive in whether some action is taken or not, either through a set of actions that can signal certain acceptance or support, or as a form of political support from the grass roots. (shrink)