Definition
Apostacy (also spelled apostasy) is a historical English legal term denoting the total, formal renunciation of Christianity. As a legal offense, it applied only to those who had previously professed the Christian faith and who subsequently abandoned it — either by adopting another religion or by embracing no religion at all. It did not apply to persons who had never been Christian. The term belongs exclusively to the legal history of England under a regime of established religion; it has no operative meaning in modern Anglo-American law.
Common Language
Modern common usage (Wiktionary): Archaic form of apostasy — the abandonment or renunciation of a religious belief or faith.
Historical common usage (Webster's 1913): "An abandonment of one's religious faith, political party, moral allegiance, or the like."
The gap between common and legal meaning is significant in one direction. Ordinary usage treats apostasy as any departure from any religion or deeply held commitment. The legal definition in English law was considerably narrower: it was confined to renunciation of Christianity specifically, by persons who had previously professed it, and it was enforceable as a criminal offense under English statute. The breadth of the common meaning obscures the law's denominational specificity and its punitive character.
Common Confusion
Apostacy is frequently confused with heresy and blasphemy, which were related but distinct English ecclesiastical and common law offenses. Heresy involved holding incorrect doctrinal beliefs while still nominally within the Christian church. Blasphemy involved speaking against God, Christianity, or the scriptures. Apostacy required complete departure from Christianity altogether. The three offenses occupied different places in the hierarchy of religious crimes and carried different legal consequences at different periods. Researchers conflating these terms will retrieve different bodies of authority and different statutory treatment.
Why It Matters in Research
This term is a reliable marker of a specific historical legal regime, not a living doctrine. Its presence in a source signals either pre-nineteenth-century English law or a comparative treatment of religious offense.
Several research traps apply. First, the spelling variation is consistent: apostacy and apostasy appear interchangeably across sources, including within the same edition of Black's. Corpus searches must run both forms. Second, the offense was formally abolished in England by the Ecclesiastical Jurisdiction Act 1677 and its successors, and was substantially defanged long before formal repeal; a source citing apostacy as a current offense is almost certainly historical. Third, American law never recognized apostacy as a criminal offense — the First Amendment foreclosed this from the founding — so any American authority on the term is either purely definitional (as in these dictionaries) or arises in comparative or historical context. Fourth, researchers working on establishment clause history, blasphemy law, or the English roots of American religious freedom doctrine will encounter apostacy as part of a cluster of offenses that helped define what disestablishment was meant to abolish. Tracking apostacy alongside heresy and blasphemy through English reports and commentaries illuminates that lineage.
Historical Dictionary Support
The three source dictionaries — Black's 1st, Black's 2nd, and Burrill's — are in complete and verbatim agreement, reproducing the same definition with identical citations to Blackstone's Commentaries (4 Bl. Comm. 43) and Stephen's Commentaries (4 Steph. Comm. 231). This uniformity reflects the term's settled historical character: by the time these dictionaries were compiled, apostacy was already an antiquarian entry, not a contested legal question. None of the three dictionaries extends the definition beyond the English law context or acknowledges the American constitutional bar. The absence of any American authority in these entries is itself informative — it signals that the compilers found nothing to cite because there was nothing to cite. Researchers should treat these entries as accurate descriptions of English legal history and as silent on American law.
Blackstone's treatment (cited in all three sources) presents the offense as part of a larger category of crimes against religion, grouped with heresy and blasphemy and measured against the backdrop of the Test Acts and the penal laws directed at non-conformists and Catholics. Stephen's Commentaries, written later and with greater awareness of reform, reflects the declining practical enforcement of the offense. Neither source should be read as describing a vigorous enforcement regime even for its own era.
Jurisdictional Note
Apostacy as a criminal offense is a feature of English law under an established church and has no equivalent in United States federal or state law. First Amendment free exercise and establishment clause doctrine renders such an offense constitutionally impermissible in the American system. Researchers encountering the term in American sources will find it in historical dictionaries, comparative treatments, or disestablishment scholarship — not in operative American jurisprudence.