William Jackson opens his first letter by declaring a wish to strike "out of the beaten track," a phrase that sets the tone for the entire volume. The letters are not personal correspondence but crafted essays on topics ranging from the force of custom to musical catches, painting, and the English language. Jackson adopts the persona of a retired observer whose retirement "will naturally give an air of peculiarity to my sentiments." This framing allows him to critique contemporary taste and intellectual habits with a blend of irony and directness, as when he notes that custom, "unassisted by truth, has worked the greatest miracles." The epistolary form is a deliberate choice: the advertisement admits that whether these are real letters is "a point of no great consequence," and that the physic matters more than the form.

Custom as a Target

Jackson's first letter establishes custom as his primary antagonist. He argues that custom can sanctify "nonsense in all the arts, sciences, and even religion itself." The phrasing is deliberately provocative, and he urges his correspondent to "divest yourself of the partiality acquired by habit." This is not a neutral observation; Jackson is setting up a method of skeptical inquiry that runs through the collection. He does not claim that all custom is bad, but that its force is so great it can make falsehood seem true. The letter on "The Force of Custom" thus serves as a methodological preface, warning readers that many received doctrines will be attacked. Jackson's diction is precise: he speaks of "prejudice" and "partiality" as obstacles to clear judgment, and he positions himself as a solitary truth-teller whose retirement gives him a clearer view.

The Catch and Its Defenders

Letter X, "On Catches," is one of the most vivid in the volume. Jackson describes the catch as a musical form that "in a manner owed its existence to a drunken club." He paints a scene of "savage folly" where singers depart from pitch, speak different words simultaneously, and compete to outsing each other. The language is deliberately harsh: he calls it a "scene of savage folly" that would not disgrace "the Hottentots." Yet Jackson is not merely condemning; he notes that catches flourished in the reign of George III despite the age's refinement. He accuses modern composers of producing imitations of ancient catches that "betray itself, within three bars, to be modern." The digression on Rowley's Poems shows his wider concern with authenticity and anachronism. He ends the letter with a wry postscript, acknowledging that his correspondent may like catches and inviting revenge.

Analogies Across the Arts

Jackson frequently draws parallels between different arts. In Letter XVII, "On the Analogy of the Arts," he argues that painting, music, and poetry share underlying principles. This is not a systematic treatise but a series of observations grounded in specific examples. He compares the use of parentheses in writing to certain musical effects, and he criticizes "temporary taste" that elevates fashion over substance. His method is associative rather than deductive; he moves from a remark about Corelli and Handel to a comment on modern performers who are "more elegant, tho' less solid." The analogy serves to reinforce his central claim that judgment should be based on intrinsic qualities, not on custom or novelty. Jackson's voice remains conversational, but his references to specific composers and painters show a well-informed mind.

The Epistolary Persona

The letters are addressed to an unnamed correspondent, and Jackson uses this relationship to create a sense of intimacy and directness. He often anticipates objections, as when he writes, "Forgive me this digression, but indeed I have nearly finished my subject and letter." The persona is that of a retired gentleman who is both learned and slightly eccentric. He claims to "pretend to no more delicacy than that of the age I live in," yet he is clearly more refined than the catch-singers he condemns. The advertisement's playful dismissal of the letters' authenticity—"the invention of a story to shew how they came into the editor's hands is by no means difficult"—adds a layer of irony. Jackson is aware that his observations may be taken as peculiar, but he insists that if "the physic be wholesome, it is no matter under what form it is administered."

Jackson's letters reward readers who enjoy pointed, opinionated criticism grounded in specific examples. The volume is best approached as a series of essays rather than a unified argument; each letter stands on its own, and the connections between them are thematic rather than linear. Readers interested in eighteenth-century debates about taste, the relationship between the arts, or the social history of music will find Jackson a lively and often surprising commentator. His voice is distinctive—at once urbane and blunt, learned and skeptical—and his willingness to attack sacred cows makes the collection as entertaining as it is instructive.