His most important work, The History of the Decline and Fall of the Roman Empire, published in six volumes between 1776 and 1789, is known for the quality and irony of its prose, its use of primary sources, and its polemical criticism of organized religion.

Because he says so in his autobiography, it used to be thought that a penchant from his aunt for "theological controversy" bloomed under the influence of the deist or rationalist theologian Conyers Middleton (1683–1750), the author of Free Inquiry into the Miraculous Powers (1749).

The product of that disagreement, with some assistance from the work of Catholic Bishop Jacques-Bénigne Bossuet (1627–1704), and that of the Elizabethan Jesuit Robert Parsons (1546–1610), yielded the most memorable event of his time at Oxford: his conversion to Roman Catholicism on 8 June 1753.

There, he made one of his life's two great friendships, that of Jacques Georges Deyverdun (the French-language translator of Goethe's The Sorrows of Young Werther), and that of John Baker Holroyd (later Lord Sheffield).

[10] He also met the one romance in his life: the daughter of the pastor of Crassy, a young woman named Suzanne Curchod, who was later to become the wife of Louis XVI's finance minister Jacques Necker, and the mother of Madame de Staël.

[13] Upon his return to England, Gibbon published his first book, Essai sur l'Étude de la Littérature in 1761, which produced an initial taste of celebrity and distinguished him, in Paris at least, as a man of letters.

There was further, the matter of a vast utility: "The discipline and evolutions of a modern battalion gave me a clearer notion of the phalanx and the legion; and the captain of the Hampshire grenadiers (the reader may smile) has not been useless to the historian of the Roman empire.

On 18 April 1764, he and Guise set off for Italy, crossed the Alps, and after spending the summer in Florence arrived in Rome, via Lucca, Pisa, Livorno and Siena, in early October.

[19] In his autobiography, Gibbon vividly records his rapture when he finally neared "the great object of [my] pilgrimage": ...at the distance of twenty-five years I can neither forget nor express the strong emotions which agitated my mind as I first approached and entered the eternal City.

After a sleepless night, I trod, with a lofty step the ruins of the Forum; each memorable spot where Romulus stood, or Tully spoke, or Caesar fell, was at once present to my eye; and several days of intoxication were lost or enjoyed before I could descend to a cool and minute investigation.

[29] After several rewrites, with Gibbon "often tempted to throw away the labours of seven years," the first volume of what was to become his life's major achievement, The History of the Decline and Fall of the Roman Empire, was published on 17 February 1776.

Volume IV was finished in June 1784;[31] the final two were completed during a second Lausanne sojourn (September 1783 to August 1787) where Gibbon reunited with his friend Deyverdun in leisurely comfort.

But my pride was soon humbled, and a sober melancholy was spread over my mind by the idea that I had taken my everlasting leave of an old and agreeable companion, and that, whatsoever might be the future fate of my history, the life of the historian must be short and precarious.

[32]Volumes IV, V, and VI finally reached the press in May 1788, their publication having been delayed since March so it could coincide with a dinner party celebrating Gibbon's 51st birthday (the 8th).

Adam Smith told Gibbon that "by the universal assent of every man of taste and learning, whom I either know or correspond with, it sets you at the very head of the whole literary tribe at present existing in Europe.

Beckford's annotated copy of the Decline and Fall turned up in Christie's in 1953, complete with his critique of what he considered the author's 'ludicrous self-complacency ... your frequent distortion of historical Truth to provoke a gibe, or excite a sneer ... your ignorance of oriental languages [etc.]'.

[45][46] Many scholars argue that Gibbon did not in fact blame Christianity for the empire's fall, rather attributing its decline to the effects of luxury and the consequent erosion of its martial character.

[47][48] Gibbon's work has been criticised for its scathing view of the Christian church as laid down in chapters XV and XVI, a situation that resulted in the banning of the book in several countries.

Contemporary detractors such as Joseph Priestley and Richard Watson stoked the nascent fire, but the most severe of these attacks was an "acrimonious" piece by the young cleric, Henry Edwards Davis.

For example, he wrote: From the reign of Nero to that of Antoninus Pius, the Jews discovered a fierce impatience of the dominion of Rome, which repeatedly broke out in the most furious massacres and insurrections.

Humanity is shocked at the recital of the horrid cruelties which they committed in the cities of Egypt, of Cyprus, and of Cyrene, where they dwelt in treacherous friendship with the unsuspecting natives; and we are tempted to applaud the severe retaliation which was exercised by the arms of legions against a race of fanatics, whose dire and credulous superstition seemed to render them the implacable enemies not only of the Roman government, but also of mankind.

"[52] Politically, he rejected the radical egalitarian movements of the time, notably the American and French Revolutions, and dismissed overly rationalistic applications of the rights of man.

Winston Churchill memorably noted in My Early Life, "I set out upon...Gibbon's Decline and Fall of the Roman Empire [and] was immediately dominated both by the story and the style.

"I have always endeavoured," he says, "to draw from the fountain-head; that my curiosity, as well as a sense of duty, has always urged me to study the originals; and that, if they have sometimes eluded my search, I have carefully marked the secondary evidence, on whose faith a passage or a fact were reduced to depend.

"[56] In this insistence upon the importance of primary sources, Gibbon is considered by many to be one of the first modern historians: In accuracy, thoroughness, lucidity, and comprehensive grasp of a vast subject, the 'History' is unsurpassable.

In Waugh's 1950 novel Helena, the early Christian author Lactantius worries about the possibility of "'a false historian, with the mind of Cicero or Tacitus and the soul of an animal,' and he nodded towards the gibbon who fretted his golden chain and chattered for fruit.