The course seeks to offer an analysis of the most important texts of Aquinas on the Holy Spirit and His action. Following the chronological order of composition, the main passages contained in various works will be studied: his youthful Commentary on the Sentences, the Summa contra Gentiles (cf. 4CG 19-25), the theological synthesis of the Compendium of Theology (cf. I, cc. 46-47), in his more mature work the Summa Theologica (cf. I, qq. 36-38, 43) and in his Commentaries on Sacred Scripture (cf. In Sal., In Jn. c. 15, lc. 5; c. 16, lc. 4, In Ep. Pauli), as well as in his short treatises: Contra errores graecorum, esp. c. 32; De rationibus fidei, c. 4; and QD De Pot., q. 10, aa. 4-5; especially his homilies or catechetical sermons: In Symb, Two precepts; In PN and In Ave. In a brief final summary, the most important aspects of Aquinas’ Pneumatology, still relevant to our time, will be highlighted.