This prologue issue of the OAR journal addresses the notion of response while being structured by a proposition to respond. At the centre of this publication, and its impetus, is a lecture-performance by Adrian Rifkin, entitled ‘On Writing the Last Line First (One of Three Possible Titles)’. Whereas responses are usually ‘rapid’, or else rarely formally integrated in research publications (despite the enthusiasm for response and collaboration across disciplines), here the entire issue is constituted by research-based ‘responses’ to an initial prompt. These include essays, music, images, a film program, and Rifkin’s own response. Taken together, they explore and instantiate modes and means of responding, and manifest the mechanisms of an essential yet diverse process, whereby new ideas and practices set out from previously articulated ones. To see further contributions to this issue in our 'Response' section, please visit: http://www.oarplatform.com/issue/issue-zero/