Abstract
The Paschal computus is a complicated function used by the Christian church to determine the date of its most important festival, Easter day. The calculation involves, in particular, a cycle of dates predicting incidences of the full moon. The reasons for the complexity, and for the involvement of the moon at all, are far from being immediately obvious ; especially given that many other Christian festivals, such as Christmas and saints' days, are simply assigned to fixed dates in the civil calendar.
The computus was in a state of development during the A.D. third, fourth and fifth centuries. It was put into its definitive form (which it was to retain until the Gregorian calendar reform in the sixteenth century) in Rome by a man called Dionysius Exiguus in about A.D. 525. During the period of its development, the computus became something of a preoccupation with church leaders and Christian scholars ; and, perhaps a little surprisingly, it generated substantial controversy.
Analysis reveals that the computus is a highly unusual fusion of theological and scientific thought. While some of its details have been the subject of scholarly debate, there have been very few general, full-length treatments. This present inquiry seeks to present a better appreciation of the principles underlying the character and origin of the computus, and an understanding of why it developed in the way it did. It seeks, in particular, to achieve an insight into the ideas and motivations of the people who devised, refined and promoted its varying forms.