What do we mean by 'public' in public health? How ought we to conceptualise the idea of 'populayion'? Are they merely aggregation of individuals? It also includes epistemological questions such as, what methods are most appropriate for thinking about public health? How do empirical and normative issues relate to each other? Controversial ethical, political and social issues, including those relating to vaccinations, the threat of pandemics and possible restrictions to individual liberties, public health research, screening and obesiby policy should also be considered.