The subject of this monograph is not the trite and readily explicable phenomenon of ‘lapsing’ under imperial persecution, but the voluntary falling away from the Church which appears to be more frequently attested as the Church grows in power and numbers. This is not in fact so difficult to account for, since the incidence of falling away could not fail to rise with the incidence of conversion, and all the more steeply when there was some profit to be gained by insincere or lukewarm adherence. We may find it more surprising that it was only in the fourth century that apostasy was strictly defined by Christians as the practice of pagan worship after baptism, whereas homiletic and disciplinary texts before Nicaea were more concerned to protect the moral integrity and devotional zeal of those within the fold. Yet this is perhaps a natural corollary of the fact that in the New Testament apostasia signifies only defection from the Jewish law, whereas the letter to the Hebrews reprimands all sin after baptism, not idolatry in particular, as a second crucifixion of the Saviour. In his first chapter, Hornung observes that even initiation into a secret rite did not preclude other allegiances in the polytheistic culture of the Roman world, and that the nearest analogue to religious apostasy was the desertion of one medical school for another. Jewish literature of the period seems to be conscious not so much of strict apostasy as of a rising scale of unfaithful conduct, so that many who stopped short of open idolatry saw no harm in the sharing of pagan meals or the cultivation of Greek pleasures. In the second chapter, Hornung argues that the concept of the devil as the first apostate – the story is in the New Testament and the term apostata in Irenaeus – made it possible for the Church to build a fence between the servants of God and the minions of the renegade, and to argue that the pride which overthrew him was also the cause of human delinquencies which could not be ascribed to fear. It is not clear to me, however, that the Church before Hornung used this aetiology to justify the compendious definition of apostasy which is assumed in the following chapters, subtle and erudite as they are.

The third chapter commences with rulings by Basil of Caesarea and Gregory of Nyssa on the readmission of Christians who had sacrificed to false gods in the wake of a barbarian invasion. The lightening of the penalties for those who had succumbed to duress is typical of an age in which the Church was sure of its place within the empire. Pronouncements on this subject before the fourth century are scarce, and none of the texts that Hornung cites is unredacted; the canons of Ancyra in 314, on the other hand, punish the wilful apostate more severely than the victim of persecution, and permanently deprive the fallen cleric of his office, while allowing the untainted clergy some latitude in enforcing terms of exclusion from communion. The Nicene Council (325) reluctantly makes conditions for the return of the lapsed after penance, while Laodicea brings the worship of angels under the rubric of apostasy. It is not so clear (although Hornung seems to assume this) that the Council of Quinisext would have given this name to witchcraft, theatre-going, Judaizing, commensality with infidels and the other aberrations which it proscribes in its decrees of 691–2. Again, while the canons of Arles in 314 impose an everlasting ban on those who fail to repent of apostasy, the western proscriptions of divination and eating with Jews at Agde (506), of herbal sorcery at Orleans (641) and of other superstitions at Auxerre and Elvira (both of uncertain date) might be better described as measures against the adulteration of the faith. The Council of Toledo's stigmatisation of circumcision as apostasy in 633 only throws into relief the absence of any physical sanction against commensality, angelolatry or profane swearing in the conciliar legislation of late antiquity. The relevance of these texts becomes apparent only when Horning assembles passages from the codes of Theodosius and Justinian, which withhold the right of choosing one's heir not only from those who openly defect to the synagogue or pagan temples, but from every professing Christian who is found guilty of superstition or who adheres to the heresies of Apollinarius, Eutyches and the Manichaeans. In these latter cases at least, there is no conscious tergiversation, and indeed it is the purpose of the legislator, as Hornung observes, to circumscribe the recipients of imperial favour and thus to make apostates of would-be believers. The Church, by contrast, is not so quick to exclude those who do not exclude themselves, and never imposes such an interdict without the hope of restoration after penance or at the point of death.

Whether or not the bishops in council equated all impurity with apostasy, the bishop in his pulpit proves in chapter iv to be of one mind with Hornung. John Chrysostom, for whom every lapse into superstition breaks the baptismal vow of renouncing Satan, advised his congregation to substitute hymns for pagan oaths and pious exhilaration for the mirth of drunkards staggering from the theatre. The overtures of the synagogue in Antioch appear to have been peculiarly seductive, and Chrysostom's invective scarcely distinguishes fraternisation from secession. A similar admonition that to play with Satan's tools is to be of his party is found in Caesarius of Arles, although he is no match for Chrysostom either in amplitude or in frequency of invective. Since Chrysostom was a patriarch and Caesarius presided at a number of western councils, we may take them as credible spokesmen for the principles which governed these proceedings. Nevertheless, rhetorical imputations of apostasy are not forensic judgements, and careful historians will remark that the ‘Disziplin’ which gives a title to Hornung's third chapter employs the same vocabulary, but not with quite the same timbre, as the ‘pastoral’ declamations which he samples in the fourth.