He was born to William and Cecelia Deacon. After his mother married the non-juror bishop Jeremy Collier, the young Deacon was introduced to many of the leading Jacobite and non-juror figures including George Hickes. Though lacking a university education, Deacon became an accomplished scholar and was ordained by Jeremy Collier to the nonjuring priesthood in 1716. In addition to his theological studies, Deacon studied medicine with Dr. Richard Mead (1673–1754).
He served several non-juror congregations in London before moving to Manchester around 1722, where he became a leading physician and married his wife Sarah (died 1745). Three of his twelve children served in the Jacobite rising of 1745. The oldest, Thomas Theodoras, served as captain of the Jacobite Manchester Regiment and was executed. His brother Robert Renatus died in prison and Charles Clement was exiled to Jamaica where he died in 1749. His daughter Sarah Sophia (1731–1801) married William Cartwright, an apothecary and later a Non-juring bishop in Deacon's chruch.
During his years in Manchester, the city became a significant hub of Jacobite and Non-juror activity. Though he was clearly a Jacobite, he gave his primary attention to creating a continuing Non-juror church. He strongly espoused ecclesial independence from the state and opposed reunion with the Church of England. Joining him in his efforts were Collier, Thomas Brett and Roger Laurence, all of whom participated in the Usages Controversy that divided the Nonjuring community.
The Usages party, freed from the oversight of the established church, advocated the reintroduction of four elements to the Eucharist — the invocation of the Holy Spirit, the oblation, the mixed chalice, and the prayers for the dead. The first effort at creating such a liturgy was published in 1718, with the liturgy being drafted by Deacon and Brett. Many Non-jurors, even some who thought the usages acceptable, thought that this effort came at an inopportune time. Brett would later rejoin the main Non-Usages party in 1732, but his partner, Deacon, remained true to his belief that the Usages were a necessary part of the true and efficacious Eucharist. Scottish bishop Archibald Campbell would consecrate Deacon and Laurence as bishops of what now became the Orthodox British Church (1733).
Deacon's interest in liturgics and spirituality are evidenced in his Compleat Collection of Devotions (1734). This book included a new liturgy, "The Order of the Divine Offices of the Orthodox British Church", which replaced the earlier one from 1718. In this liturgy Deacon added other ancient liturgical practices including infant communion. The book also included excerpts from John Wesley's `Essay upon the Stationary Fasts'. Wesley met Deacon through John Clayton of Manchester who had been part of Wesley's Oxford group, which led to the invitation of the future Methodist founder to contribute to the book. Though never becoming an official Anglican liturgy, Deacon's incorporation of ancient Christian liturgies and reclaiming of the doctrine of eucharistic sacrifice would influence later liturgical developments.
His most important work A Full, True, and Comprehensive View of Christianity (1747) included two catechisms, a detailed theological commentary on the Compleat Collection of Devotions, and the development of a sacramental theology that extended the number of sacraments to twelve. Among the offices added were confirmation, marriage, ordination, and infant communion.
Deacon died on 16th February 1753 and was buried in the churchyard of Manchester's St. Ann's church. His graveslab still remains.
- Henry Broxap, The Biography of Thomas Deacon (1911)
- Robert Cornwall, "Thomas Deacon", Oxford Dictionary of National Biography, (2005)
- Robert D. Cornwall, `The Later Nonjurors and the Theological Basis of the Usages Controversy', Anglican Theological Review, 75 (1993), 166-86
- W. J. Grisbrooke, Anglican Liturgies of the Seventeenth and Eighteenth Centuries,(1958).