This book, which is underpinned by a database of all the rhymes in c. 925 courtly love lyrics produced between 1300 and 1579, demonstrates that rhyme is far from being a superficial decorative feature: instead rhyme fundamentally determines and structures subject-matter. The book focuses in particular on the relationship between rhyme and the ideas about love in courtly lyrics between 1300 and 1579, spanning the periods traditionally divided into 'medieval' and 'early modern'. Concentrating on the rhyme-groups surrounding the words 'pain', 'woe', and 'heart', it argues that the limited rhyme resources of English render certain clusters of words and ideas almost inevitable, particularly in forms like the ballade and the roundel, which are hungry for very large rhyme-groups. The result is that groups of ideas which are linked by the essentially arbitrary element of rhyme come to determine the characteristics of love in poetry, while the impression of subjectivity emerges as a side-effect of rhyme's requirements.The book is controversial in its argument that content is a side-effect of form, and poses fundamental challenges to the critical status quo. Although a handful of earlier critics like Hugh Kenner have raised the idea of the constitutive power of rhyme, this has never been the subject of a monograph, and this book is unique in its marrying of these ideas with a data-driven approach. In its distinctive way, it contributes to the ongoing critical movement which aims to break down period boundaries between the medieval and early modern. It allows the study of often-neglected material, and it also maps aspects of the literary landscape inherited by poets like Sidney, Spenser, and Shakespeare.