Richard Polwhele explains in his Advertisement that Sir Aaron was extracted from a longer poem called The Saint's Progress or the Mysteries of Methodism in seven cantos, in a variety of measures, a precedent for which could be found in Alexander Thomson's allegorical Paradise of Taste (1796). After debating whether to adopt a uniform or variable stanza, he laid aside the poem, only to take it up again: "he determined in favour of 'a Uniform,' and fixed on the stanza of Spenser. But, in adopting this stanza, he was induced to alter the very plan and conduct of the poem" p. 143. The "most respectable correspondent" giving hints for the construction of the poem was likely James Hurdis: a letter of his concerning Sir Aaron, dated 8 January 1800, appears in Polwhele's Traditions and Recollections (1826) 519.
Polwhele had published Anecdotes of Methodism (1800) which was answered in Methodism tried and acquitted (1800) and in Samuel Drew's Observations in behalf of the Methodists (1800). Several replies and answers followed; see Boase and Courtney, Bibliotheca Cornubiensis (1874-82) 2:510.
John Gifford to Richard Polwhele: "I mean to publish, on the first day of every year, a pocket-volume, to be entitled, 'The Spirit of Anti-Jacobinism,' as an antidote to Philips's 'Spirit of the Public Journals.' I do not mean it to be political entirely, nor even principally, but to contain a well-chosen collection of poetical pieces, and prose essays, and dissertations on various subjects, literary, moral, controversial, &c. &c. Some sheets of that for January next are printed; and if you have any thing in prose or verse that will meet it, I shall be obliged to you for it, and will allow the same price as for matter supplied for the Review. The 'Saint's Progress' would, I think, appear there to advantage. Have you not an essay on the Pastorals of Theocritus, and some other prose compositions which might be inserted in this little volume too?" 28 September 1800; Polwhele, Traditions and Recollections (1826) 2:518.
With the view of exposing to the ridicule, contempt, and detestation which they deserve, the extravagance and effrontery of religious enthusiasts and hypocrites; the Author had written, about a twelve-month ago, a mock heroic poem, entitled THE SAINT'S PROGRESS; OR, THE MYSTERIES OF METHODISM. It consisted of seven cantos; in each of which the measure of the poem was varied. Though, in the judgment of some persons, this variety had its use, precluding that languor which is often occasioned, even in skillful hands, by the monotony of a uniform stanza; yet, in the apprehensions of others, it destroyed the effect of the composition, as a whole; since every new canto, so totally unlike its neighbour, had the appearance of an independent piece. "Mr. Alexander Thompson's" different meters were instanced; and termed "heterogeneous substances; never approaching the points of contact, but reciprocally repelling each other." [Author's note: Mr. P. should by no means be able to reconcile himself to himself, if he were to let this slighting notice of Mr. Thompson pass, without adding his own sentiments — which are, that Mr. T. is a man of very fine imagination — in short, that he is one of the first poets of the day.] Suspended therefore between these two opinions the Author threw aside his poem.
Yet, being lately reminded of the manuscript and furnished with several hints for a new construction of the poem, by a most respectable correspondent (whose countenance would reflect a distinguished lustre on the first literary character) he determined in favour of "a Uniform," and fixed on the stanza of Spenser. But, in adopting this stanza, he was induced to alter the very plan and conduct of the poem.
In THE SAINT'S PROGRESS; OR, THE MYSTERIES OF METHODISM, is attempted a ludicrous description of the Methodists, from their first sudden conversion, to their ultimate state of unsinning perfection. But, in SIR AARON; OR THE FLIGHTS OF FANATICISM, are represented, I. The character of a young gentleman of distinction — his eccentric imagination — his ungovernable passions — his conversion to Methodism. — II. The wild visions of his fancy — his ideal pilgrimage to hell. — III. And the fatal effects of his fanaticism, with regard to himself, his family, and his neighbourhood. Thus the three cantos of the present poem may be presumed to form a complete whole; whether its design, its structure, or its sentiments be considered.
That the reader may conceive some idea of the execution of the first performance, a few extracts from it, are subjoined in the notes. The greater part of the sixth canto of THE SAINTS PROGRESS, is brought into the service of SIR AARON; forming the second canto.