This was the turning-point of his life. He was sent to a Calvinist minister at Lausanne, who treated him with such tact that the articles of his Catholic creed "disappeared like a dream." Like a dream, however, disappeared also all higher impulse. Thenceforward Gibbon was known simply as an earthly-minded scholar, warm-hearted, but flippantly sceptical of every religious aspiration. He remained for five years at Lausanne, gaining a breadth of culture, through his knowledge of French, such as he could never have attained in England. Towards the end of the time he fell in love with Mdlle. Curchod, the daughter of a pastor, but finding that his father objected to the match, "sighed as a lover" and "obeyed as a son." This was the only ripple of passion which crossed the complacency of his egoism, and it was easily calmed. The lady seems to have retained hopes of the marriage until his next visit to Lausanne in 1763, when his coldness put it out of the question. She married the French minister, Necker, but retained a tender feeling for Gibbon until the end of his life. In a letter, written a month before his death, she spoke of "the sentiment which links my soul for ever to your own."
On his return to England, Gibbon lived partly at his father's estate in Hampshire, where he joined the militia. This force was embodied in 1760, and for two years Captain Gibbon was constantly in camp. In 1761 he published a treatise in French, Essai sur l'Etude de la Litterature, and was already meditating the employment of his powers upon some more serious task. Freed from the militia, be went abroad, spent nearly a year at Lausanne, studying the antiquities of Italy, and then visited Rome. It was on the 15th of October, 1764, that, while seated among the ruins of the Capitol and hearing vespers sung by friars in the Temple of Jupiter, he conceived the design of writing the history of the decline and fall of the city, which, however, he did not set about until four years later. Meanwhile he worked with his friend, Deyverdun, at the history of the Swiss struggle for independence, a subject which he finally abandoned. In 1767 and 1768 he helped the same friend to produce a periodical, Memoires Litteraires de la Grande Bretagne, and in 1770 he brought out anonymously Critical Observations upon the Sixth Book of the AEneid, an attack upon Warburton's theory of Vergil's under-world. In 1774 he entered Parliament for Liskeard, and two years later published the first volume of the History of the Decline and Fall of the Boman Empire. Its success was immediate and startling, but the chapters upon the causes of the spread of Christianity created an outcry, which led Gibbon to bring out a Vindication in 1779. In the same year he was appointed to a sinecure office in the Board of Trade, in reward for his "sincere and silent vote" in favour of Lord North, and also, we may suppose, for a Memoire Justificatif which he had drawn up in reply to a French manifesto. In 1780 he lost his seat, but reentered Parliament as member for Lymington in 1781, in which year he published the second and third volumes of his History. In 1782 his sinecure was abolished, and before long he determined to take up his abode with Deyverdun at Lausanne, a town which became his home for the remaining ten years of his life. In 1788 his fifty-first birthday (8th May) was marked by the publication of the last three volumes of the Decline and Fall. Upon this book Gibbon's fame must chiefly rest. Written with the imperfect views of the last century upon the development of civilisation, it has, nevertheless, kept its place without a rival. The project was vast, the ground untrodden, but the encyclopaedic knowledge, the keen insight, and brilliant imagination of Gibbon enabled him to give a vivid and enduring picture of men and scenes, and a comprehensive summary of the ages of strife by which the modern world was shaped upon the ruins of the old. As an historian, Gibbon stands almost alone in the skill with which he groups the various parts of his book, and in his capacity for taking broad views of principles and actions while discussing the most minute points with the accuracy of a trained and careful scholar. His style, which in his youth completely fascinated Cardinal Newman, the greatest recent master of varied prose, although artificial and monotonous, is well adapted, in its stately and sonorous march, to the magnitude of the events which it describes.
Such was the great work of Gibbon's life, which, on its publication, was already drawing near its close. In 1793 he was in England, when the rapid development of a long-neglected evil (hydrocele) forced him to seek medical advice. It was, however, too late, and he died on the 15th January, 1794. After his death, his Memoirs - a brilliant, though incomplete, autobiography - were published by his friend, Lord Sheffield, together with his correspondence and a number of essays upon historical and classical subjects.