In 1751 the papal nuncio, Archinto, visited Nothenitz, and in 1754 Winckelmann joined the Roman Catholic Church. Goethe stated that Winckelmann was a pagan, but his conversion finally opened the doors of the Pope's library to him. He was named librarian to Domenico Cardinal Passionei, who was impressed by Winckelmann's beautiful Greek writing. After publishing
Gedanken über die Nachahmung der Griechischen Werke in der Mahlerey und Bildbauer-Kunst, Winckelmann moved to Rome.
Augustus III, king of
Poland and elector of Saxony, granted him a pension of 200
thalers, so that he might continue his studies in Rome.
He arrived in Rome in November 1755. His first task in Rome was to describe the statues in the
Cortile del Belvedere — the
Apollo Belvedere, the
Laocoön, the so-called
Antinous, and the
Belvedere Torso — which represented to him the "utmost perfection of ancient sculpture." He became librarian to Cardinal Archinto, and received much kindness from
Cardinal Passionei. After their deaths, Winckelmann was received as librarian and as a friend into the house of Cardinal Albani, who was forming his magnificent collection of antiquities at
Porta Salara, and became his patron.
Originally Winckelmann planned to stay in Italy only two years with the help of a grant from Dresden, but the outbreak of the
Seven Years' War (1756-1763) changed his plans.
He devoted himself earnestly, at first with the aid of his new friend, the painter
Anton Raphael Mengs (1728-79), whom he first met in Rome, to the study of Roman antiquities and gradually acquired an unrivalled knowledge of ancient art. Mengs became the channel through which Winkelmann's ideas were realized in art and spread around Europe. "The only way for us to become great, yes, inimitable, if it is possible, is the imitation of the Greeks," Winckelmann declared. With imitation he did not mean slavish copying: "... what is imitated, if handled with reason, may assume another nature, as it were, and become one's own." Winckelmann discredited Roman art, which was unusual at that time — Roman culture was considered the ultimate achievement of Antiquity. Neoclassical artists attempted to revive the spirit as well as the forms of ancient Greece and Rome. Mengs's contribution in this was considerable — he was in his day widely regarded as the greatest living painter. The French painter
Jacques-Louis David met Mengs in Rome (1775-80) and was introduced to the artistic theories of Winckelmann.
In 1760 his
Description des pierres gravées du feu Baron de Stosch appeared, followed by his
Anmerkungen über die Baukunst der Alten ("Observations on the Architecture of the Ancients") in 1762, which included an account of the temples at
Paestum. In 1758 and 1762, he visited
Naples to observe the archaeological excavations being conducted there. Usually the excavations of
Pompeii (1748) have been considered the decisive stimulus to the new archaeological classicism, but the excavation of
Herculaneum took place much earlier. These two cities had been buried by an eruption of Mount Vesuvius in A.D. 79.
Winkelmann's study
Sendschreiben von den Herculanischen Entdeckungen (Letter About the Herculanean Discoveries) was published in 1762, and two years later
Nachrichten von den neuesten Herculanischen Entdeckungen (Report About the Latest Herculanean Discoveries). From these scholars obtained their first real information about the treasures excavated at
Pompeii and
Herculaneum.
His major work,
Geschichte der Kunst des Alterthums (1764, The History of Ancient Art), deeply influenced contemporary views of the superiority of Greek art. It was translated into French in 1766 and later into English and Italian. Among others, Gotthold Ephraim Lessing based much of the ideas in his 'Laokoon' (1766) on Winckelmann's views on harmony and expression in the visual arts. Lessing also stated that painting uses completely different means or signs than does poetry, which depicts progressive action rather than the visible and stationary. From 1763, while retaining his position with Albani, Winckelmann worked as a prefect of antiquities (Prefetto delle Antichità) and scriptor (Scriptor linguae teutonicae) of the Vatican. Winckelmann again visited Naples, in 1765 and 1767, and wrote for the use of the electoral prince and princess of Saxony his
Briefe an Bianconi, which were published eleven years after his death, in the
Antologia romana.