This thesis involves the submission of published academic work with a critical commentary, in accordance with the regulations of the University of the West of England on Supervised DPhil degrees. Nine papers are submitted, published from 1998 to 2013. Although their subject matter is diverse, I argue in the critical commentary that the work is concerned with critical organizational history and historiography, counterfactuals and modality, and connections, boundaries and identity. The works submitted are theoretical rather than empirical in nature (hence 'theory' in the thesis title) and are thematically connected either by a focus on practice (academic practice, or in and around organizations more generally; hence 'practice'), or by a concern with connecting separate bodies of theory or disciplinary areas (hence 'boundary work'), or both. There are also common themes connecting the papers, in as much as organizational history - broadly conceived as the connection between the organizational past and present, and its interpretation, representation, and so on - and strategy (traditionally and historically concerned with organizational action which connects the present to the future) remain a major focus. The second clause of the thesis title is intended to reflect these concerns. In the introduction to the commentary I briefly comment on the title of the thesis and its relation to the selected papers, list the papers selected for the thesis, and outline the structure of the commentary. I then discuss in the second major section of the commentary, the background to the studies, their themes, and their originality and significance. In a sub-section, I briefly reflect upon their influence and impact, referring among other things to citation data presented as part of the commentary. I then provide a methodologically informed account of the papers, describing and assessing the extent of research competence displayed, as well as discussing the approaches to theory and theorising in the different papers presented. Finally, I clarify, on a paper by paper basis, my personal research contribution to each of the studies, before concluding the commentary with a final reflection on the work submitted.