Mariology
Before Vatican II, Tromp engaged in a debate with Gabriel Roschini regarding the position of Mary in the Mystical Body of Christ.
Roschini demonstrated that numerous writers, starting with Radulfus Ardens (d. 1200), used the metaphor of a "neck" to indicate Mary's role, and that even the Protestant reformer Johannes Oecolampadius used that image to describe Mary as mediator of all graces. (The neck had been used through the centuries as an allegory for vital communication within the body.) Roschini quoted Bernardino of Siena (d. 1444) to that effect: "Mary is the neck of our head, through which all gifts are given to his mystical body." Pope Pius X also considered the neck to be the best image, observing as much in his 1904 encyclical Ad diem illum.
Tromp, however, considered the heart, the superior of all parts of the body, a better image. In his defense, he quoted Thomas Aquinas and Pope Leo XIII. According to Tromp, the heart, being in so many ways incomparable to the other parts of the body, parallels the fact that no member of the Church can be compared to Mary. The heart, continued Tromp, is consubstantial with the head and the body, just as Mary's human nature participated with that of Christ and the members of his body. Tromp concluded that because of her motherly love of Christ and of all the members of his body, she deserves to be identified with the heart.
But Roschini was categorically opposed. The heart has influence over the head, and in view of Christ's nature, this is impossible: "After giving him human nature, the Blessed Virgin has no influence whatsoever on Christ as head of the Church". In Mystici corporis, Pius XII avoided this issue, calling Mary simply the "mother" of the mystical body. She was already mother of the head, he wrote, but under the cross she was named mother of all its parts.
He was member foundatour of Pontifical Academy of Mary.
Read more about this topic: Sebastiaan Tromp, Theological Influence