This thesis explores the implications of fundamental questions of human nature for our response to our environmental crisis. It argues that the most important and unique contribution theology can make to environmental ethics is not in motivating believers to value the natural world, but in providing insight into the complexity and depth of human agency in environmental context. Much of Christian environmental ethics has understood its role to be to provide the right symbols and values to drive improved environmental behavior: if we get our theology of creation and our cosmologies right (that is, make them non-anthropocentric), then right action will follow. I argue that this approach begs significant ethical, theological, and practical questions. It assumes that there is a straightforward connection between theological ideas and behavior in the world and it assumes that theological ideas can be manipulated voluntarily to produce desired behavioral outcomes. This is a simplistic picture of the operation of the levers that move human history. I seek to demonstrate that an advantage of religious ethics has been precisely the fact that it rejects such simplistic understandings of human beings. An important religious insight is that we are complex, even paradoxical, amalgamations of competing wills, desires, powers, and propensities. It is more fitting to turn to religion, I argue, not for uniquely evocative symbols to fix our environmental problems, but for a sense of the ambiguity and depth of the challenges of the human condition, including our environmental situation. Building on the work of Reinhold Niebuhr, I argue that a Christian realist perspective on the structure, drivers, and limits of human history allows for a more coherent interpretation of environmental problems than alternative approaches. Such coherence, I argue, forms the basis of more realistic and responsible environmental agency.