In this important book Niklas Luhmann - one of the leading social thinkers of the late 20th century - analyses the emergence of 'love' as the basis of personal relationships in modern societies. He argues that, while family systems remained intact in the transition from traditional to modern societies, a semantics for love developed to accommodate extra-marital relationships; this semantics was then transferred back into marriage and eventually transformed marriage itself. Drawing on a diverse range of historical and literary sources, Luhmann retraces the emergence and evolution of the special semantics of passionate love that has come to form the basis of modern forms of intimacy and personal relationships. This classic book by Luhmann has been widely recognized as a work of major importance. It is an outstanding contribution to social theory and it provides an original and illuminating perspective on the nature of modern marriage and sexuality.