So-called threatening letters were a form of media, frequently produced in agrarian social conflicts in eighteenth-and nineteenth-century Ireland. This thesis analyses a collection of such letters, or notices, as a means of accessing the subjectivities of some of the participants in those conflicts. The production of the notices is associated with a series of peasant-based social movements, generically known as whiteboys, which existed circa 1760 to 1850. The specific collection of notices examined in this thesis was amassed by the state authorities in the eastern province of Leinster in the year 1832. The thesis is divided into three parts. The first section addresses the contexts within which the notices were generated. I argue that a central part of those contexts was, at least by the early-nineteenth-century, a stalled transition from the feudal to capitalist modes of production. In part then the threatening letters were part of a resistance to primitive accumulation and proletarianisation. The main body of this study is concerned with analysing the content of a selection of notices using a methodology adapted from ground theory method. Through a process of inductive coding I identified two themes within the notices which are scrutinised sequentially in parts II and III. These themes I have called ‘coercive regulation’ and ‘collective identity’. Coercive regulation refers to motifs the notices share with, on the one hand, customary rituals of punishment similar to the French charivari, and, on the other hand, the official legal system and other ruling class cultural uses. The latter I consider through drawing on the work of Gramsci, Vološinov, and Bakhtin to better understand relationships between elite and popular cultures. Collective identity principally refers to the use of a common set of symbols across many letters, especially when such symbols are particularly associated with another time and place, i.e. with an earlier movement or with a movement in another part of the country. This practise I interpret as a form of collective identity and I also relate it to debates on class formation. Finally, I ask why collective identity was important in the often very localised situations within which the notices were used. In answering this I advance a proposition linking collective identity and collective efficacy and argue that a sense of collective identity reinforces a sense of collective efficacy.