Leo I’s jurisprudence should be understood against the background of the earlier papal rulings available to him in the archive. He could not assume that these rulings would be generally known outside Rome, though they were being passed around. For that reason as well as for emphasis, repetition of earlier decisions was in order, but Leo I tended to draw out their logic and explain their rationale more fully than his predecessors had done. He worked within the already well-defined paradigm created by the first half-century of papal jurisprudence. Issues he dealt with included baptism’s relation to the liturgical year, the implication of penance for subsequent careers, indissolubility of marriage, pollution and celibacy, election of bishops and hierarchy.

In the late Roman Empire, complexity and uncertainty created demand for responsa from the apostolic see. After the eleventh-century papal turn, new legislation and a different society generated new complexities and uncertainties. Decretals were not the only way to resolve them, but given the prominence of the tradition launched by Siricius and Innocent I, they were an obvious way. An unbroken chain of communication links the first and second decretal ages. Late Antiquity and the central Middle Ages need not be kept in separate compartments.

The book attempts a long-range history which is about expansion of meaning in the course of reception, and the kind of social soil in which papal jurisprudence flourished in periods widely separated in time.

The fourth chapter analyses what scholars have called ‘symbolic’ or ‘heavenly’ coronations in Byzantium. With the expansion of Christianity throughout the Mediterranean, self-coronation and the mediation of priests became a point of divergence. Emperors in Christian Byzantium are to be crowned by the patriarchs in ritual practice, but they are frequently crowned by the iconographic representation of the ‘hand of God’. This chapter engages in a comparative analysis of the reality of church intervention in the real performative ceremony of the imperial coronation and the imaginative fiction of the crowning of the emperor directly by Christ and his angels and saints, as established in some iconographic representations. In Byzantium, imperial art was given the task of translating into a visual and symbolic – but not necessarily referential – language the values and ideology that prevailed in each dynasty concerning the source of its power.

‘Bigamy’ – the ban on twice-married men or husbands of widows becoming clerics – was another way of marking out the clergy from ordinary people. For the latter, remarriage after the death of a spouse was unproblematic, but it was an absolute bar to a clerical career. The underlying rationale takes one deep into the realm of symbolism.