 Morally responsible public health policy requires attentiveness to the multiple determinants of health. This requirement does not signal that public health has no boundaries. Rather, public health has a unique relationship of stewardship to health, and to the particular determinants that have a special strategic significance for health. Some of those determinants are the classic focus of public health, such as infectious disease control and the securing of safe food, water, and essential medications. However, exercising that stewardship requires responsiveness to the best available evidence about all the determinants, across the landscape of an interconnected social structure, that have a special strategic relation to health. These determinants often lie outside the conventional remits of public health agencies and authorities. Policies governing education, foreign assistance, agriculture, and the environment can all have a significant impact on health, just as health policies can impact international relations and national and global economies. 