This chapter looks at two ways that contemporaries sought to deal with the fundamental unpredictability of the dynastic world. The scientific approach was to look for predictions in the stars, and astrology was a learned practice in many of the courts of the medieval world. There are surviving horoscopes for many medieval monarchs and astrologers received the patronage of such rulers as Manuel Comnenus, Frederick II and Alfonso the Wise. A tradition of Christian criticism of astrology did not make much impact on this courtly obsession. A less scientific method of divining the future was to have recourse to prophecies and visions, either those of contemporary visionaries or those recorded in ancient books. The Vision of Charles the Fat is analysed in detail as an example of the former, the Prophecies of Merlin as an example of the latter. Merlin’s prophecies spread throughout Europe and generated a large body of interpretation. They offered a tempting key to dynastic events, and their ambiguity meant they could be continually adopted to new situations and given new meanings. The chapter concludes with the case study of Eleanor Cobham, duchess of Gloucester, who efforts to divine the dynastic future brought about her downfall.