This conversion is, on the whole, the most surprising incident of his calm and uneventful life. The tendencies of the time, both in England and on the Continent, were in a wholly different direction. The more spiritual and emotional natures were now passing into the religious revival of Wesley and Whitefield, which was slowly transforming the character of the Anglican Church and laying the foundations of the great Evangelical party. In other quarters the predominant tendencies were towards unbelief, skepticism, or indifference. Nature seldom formed a more skeptical intellect than that of Gibbon, and he was utterly without the spiritual insight, or spiritual cravings, or overmastering enthusiasms, that produce and explain most religious changes. Nor was he in the least drawn towards Catholicism on its aesthetic side. He had never come in contact with its worship or its professors; and to his unimaginative, unimpassioned, and profoundly intellectual temperament, no ideal type could be more uncongenial than that of the saint. He had however from early youth been keenly interested in theological controversies. He argued, like Lardner and Paley, that miracles are the Divine attestation of orthodoxy. Middleton convinced him that unless the Patristic writers were wholly undeserving of credit, the gift of miracles continued in the Church during the fourth and fifth centuries; and he was unable to resist the conclusion that during that period many of the leading doctrines of Catholicism had passed into the Church. The writings of the Jesuit Parsons, and still more the writings of Bossuet, completed the work which Middleton had begun. Having arrived at this conclusion, Gibbon acted on it with characteristic honesty, and was received into the Church on the 8th of June, 1753.
The English universities were at this time purely Anglican bodies, and the conversion of Gibbon excluded him from Oxford. His father judiciously sent him to Lausanne to study with a Swiss pastor named Pavilliard, with whom he spent five happy and profitable years. The theological episode was soon terminated. Partly under the influence of his teacher, but much more through his own reading and reflections, he soon disentangled the purely intellectual ties that bound him to the Church of Rome; and on Christmas Day, 1754, he received the sacrament in the Protestant church of Lausanne.