Book excerpt: Pope John Paul's Theology of the Body catecheses has garnered tremendous popularity in theological and catechetical circles. Students of the Theology of the Body have generally interpreted it as innovative not only in its presentation of the Church's teaching on marriage and sexuality, but also as radically advancing that teaching. Aquinas and the Theology of the Body offers a somewhat different interpretation. Fr. Thomas Petri argues that the philosophy and theology of Thomas Aquinas substantially contributed to John Paul's intellectual formation, which he never abandoned. A correct interpretation of the Theology of the Body requires, therefore, a thorough understanding of Thomistic anthropology and theology, which has been mostly lacking in commentaries on the pope's important contributions on the subject of marriage and sexuality.