This thesis examines the complex textual history of Sei Shonagon's Makura no soshi, an 11th century text. It describes and compares the four main textual lineages of the work, Noinbon, Sankanbon, Maedakebon and Sakaibon, and summarizes the debates among Japanese scholars concerning the issue of authenticity. This thesis defends the consensus of centuries of readers and modern scholarship that the two textual lines organized in random order, the Noinbon and the Sankanbon, represent the version closest to the original text. Detailed textual analysis is performed on passages that vary between the Sakanbon and Noinbon, focusing particularly on the work's "epilogue." On the basis of that analysis, this thesis proposes that the sense of temporal proximity, intimacy, and spontaneity apparent in the narrative style of the Noinbon make it the best candidate for the most authentic manuscript line.