Background
Many public health practitioners and organizations view themselves as engaged in the promotion or achievement of equity. However, discussions around public health frequently assume that practitioners and policy-makers take a utilitarian approach to this work.

Methods
I argue that public health is better understood as a social justice endeavor. I begin by presenting the utility view of public health and then discuss the equity view. This is a theoretical argument, which should help public health to justify interventions for communicable and non-communicable diseases equally, and which contributes to breaking down the ‘old/new’ public health divide.

Results
This argument captures practitioners’ views of the work they are engaged in and allows for the moral and policy justification of important interventions in communicable and non-communicable diseases. Systemic interventions are necessary to remedy high rates of disease among certain groups and, generally, to improve the health of entire populations.

Conclusions
By viewing diseases as partly the result of failures of health protective systems in society, public health may justify interventions in communicable and non-communicable diseases equally. Public health holds a duty to improve the health of the worst-off in society; by prioritizing this group, the health of the whole community may improve.