Right from the start they decided to adopt the Ethiopian style of dress and accommodate themselves to Ethiopian food. They set about learning three languages: Amharic, the national language, Tigrina the local language of the area where they were, and Ghe’ez the liturgical language. There is plenty of contemporary evidence that Justin acquired a very good knowledge of these languages, and later on he even wrote some books in Amharic….With the exception of one young confrere, Carlo Delmonte, all Justin’s fellow-Vincentians disagreed with Justin’s missionary methods, especially with regard to indigenous clergy.

Even the confrere who was to be his coadjutor bishop, Lorenzo Biancheri, who had the right of succession, said openly that when he succeeded Justin he did not intend to continue Justin’s missionary methods, especially in the matter of building up a body of indigenous clergy.

However, as I mentioned a moment ago, Justin was proved right. He had anticipated by more than a century what Vatican II and Paul VI’s Evangelii nuntiandi would say about missiology.

See Vincentian Encyclopedia