This is a conceptual essay that explores the concept of knowledge as it relates to PR. It suggests an ecological knowledge architecture as a lens through which to understand the theories and concepts that support practice. It does so by drawing on the work of Zygmunt Bauman and his reflections on liquid modernity to inform and shape thinking and uses it as a thread to help synthesise scholarship from PR literature, knowledge and career scholarship and debates around professionalisation. It argues that by sub-dividing knowledge into explanatory, interventionist and practice principles greater clarity can be given to the know-how (functional skills) and know-that (theoretical knowledge) of PR. Additionally, by overlaying a postmodernist and liquid concept to this tripartite division of knowledge PR can be well placed to take advantage of the change in careers and capabilities necessary for work in the twenty-first century.