Composed at the request of the emperor Gratian, De spiritu sancto continues the instruction begun in DE FIDE by demonstrating the divinity of the Holy Spirit. It draws on Greek sources, especially the treatise of Didymus. The work was criticized severely by JEROME, who (according to Rufinus) accused him of writing "bad things in Latin taken from good things in Greek" (trans. in Deferrari 1963 p 32). Manuscripts of De spiritu sancto often contain Gratian's letter to Ambrose [CCSL 79.3-4]. For the Salisbury manuscript, see Webber 1992 (p 152). According James and Jenkins 1930-32 (4.572), the Lambeth Palace manuscript contains one (unspecified) excerpt.

The Fulda manuscript, headed "Incipit Fides Edita Sancti Ambrosi Episcopi De Spiritu Sancto," includes only the chapter titles of the three books (see Faller, CSEL 79.40*, CPL 151; this text was edited as if it were a separate work by Huhn 1953, reprinted in PLS 1.604-6, with corrections at PLS 1.1749). Machielsen, who does not refer to Faller or to the note by Dekkers and Gaar, lists the Fulda text as a pseudepigraph (CCPM IIA.48).

The parallel Jones cites with BEDE's COMMENTARIUS IN GENESIM (see CCSL 118A.63) is slight, but Bede does cite this work in his EXPOSITIO ACTUUM APOSTOLORUM (CCSL 121) and COMMENTARIUS IN EPISTOLAS SEPTEM CATHOLICAS (CCSL 121).