This essay reviews some of the sources of idealism in public health, on the basis of an intellectual journey to Kos (home to Hippocrates and his altruistic legacy), Dresden (where the Deutsches Hygiene Museum illustrates the historical connections between fascism and public health), and Utopia (exemplified by Etienne Cabet's Icarie, a fantasy of an ideal city which has nevertheless been partly realized). It is suggested that the large-scale altruism of public health has to be balanced with the value of individual autonomy, and that some degree of dreaming of a better and healthier world is indispensable for further progress in public health. The main conclusion is that the ethical foundations of public health are not always self-evident, and that critical reflection on these foundations was, is, and will always be necessary.