This book provides a comprehensive study of hedging in academic research papers, relating a systematic analysis of forms to a pragmatic explanation for their use. Based on a detailed examination of journal articles and interviews with research scientists, the study shows that the extensive use of possibility and tentativeness in research writing is intimately connected to the social and institutional practices of academic communities and is at the heart of how knowledge comes to be socially accredited through texts. The study identifies the major forms, functions and distribution of hedges and explores the research article genre in detail to present an explanatory framework based on a complex social and ideological interpretive environment. The results show that hedging is central to Scientific argument, individual scientists and, ultimately, to science itself. The importance of hedging to student writers is also recognised and a chapter devoted to teaching implications.