Ferdinand studied law, philosophy and theology in Ingolstadt and wanted to enter the Capuchin Order.

Marco d'Aviano prophesied his success as a priest and recommended him, after Rummel's ordination in Regensburg, to be an educator and religious tutor to the future Emperor Joseph I.

In addition, the wife of Emperor Leopold I, Eleonor Magdalene of Neuburg, favored him because his grandfather, Johann Rummel, had already served the Palatinate as a chamber councilor.

On 11 July 1706, he was appointed Prince-Bishop of Vienna by Joseph I, the Papal confirmation taking place on 4 October.

He also mediated between the Emperor and Pope Clement XI when in 1708 Austrian troops occupied territories of the Papal States during the War of Spanish Succession.