This dissertation offers a new look at the Pore Caitif, a late-fourteenth century treatise of doctrine and devotion. Taking into account recent scholarship in the field of manuscript studies, particularly `materialist philology' which focusses on the entire codex rather than a text in isolation, the dissertation seeks to elucidate some of the textual and cultural contexts of the Pore Caitif. It is argued that taking the entire corpus of miscellaneous codices containing the Pore Caitif as the point of departure for investigation can help to arrive at an understanding of the nature and the use of this variable treatise. To this end, a large number of manuscripts are investigated in detail. Fresh, and in many cases for the first time, codicological descriptions are established for the majority of manuscripts containing the Pore Caitif and a number of other related texts. The data uncovered by this exercise are then analysed with a view to elucidating a number of historical ambiguities relating to the treatise, particularly dating and doctrinal affiliations. An appendix provides a parallel text of orthodox and heterodox versions of the Ten Commandments Commentary from the Pore Caitif.