Hauntology as a successful academic concept holds a pun on the idea of ‘ontology’. It denotes a temporal nonlinearity, the persistence and lingering of failed, of omitted, often utopian, ideas that also formed radical visions of futures and opens a field to discuss presence and absence, visibility and invisibility. The present we live is embedded in the presence of ghosts and specters, and the traces of imaginations of different times and spaces may become visible and doable. The scholars and artists contributing to this volume discuss these conceptual outlines in a series of transdisciplinary contributions. Art in its various forms is the integral part of these hauntological engagements. [publisher's note]