This was a decisive experience in his professional formation, allowing him not only to gain a profound knowledge of the current practice of the courts but also to develop a critical vision of the system of jus commune.

[7] He actively participated in the cultural life of Rome and attended the meetings of several learned societies, including the Royal Academy founded by Queen Christina of Sweden in 1680.

[8] The support and protection of Nicola Herrera, the apostolic nuncio in Naples, of the Neapolitan cardinals Pier Luigi Carafa and Innico Caracciolo, and above all that of Niccolò Ludovisi, prince of Venosa, permitted De Luca to enter quickly into the most important circles at the papal court.

At an advanced age he became a priest and was made first referendary Utriusque Signaturae, then auditor of the Sacred Palace by Innocent, who finally in 1681 raised De Luca to the cardinalate.

His "Annotationes practicae ad Sacrum Concilium Tridentinum" (Cologne, 1684), a legal commentary on the decrees of the Council of Trent, became a prime authority and was reissued several times.

[2] In the introduction to this work the author argues in favor of the use of the common language in place of Latin in order to render law familiar outside the legal sphere, for the benefit of a nonprofessional readership.

[11] He reasserted his theses in two brief but important works: Dello stile legale (On the style of law, 1674) and Difesa della lingua italiana (Defense of the Italian language, 1675).