Convergences: To the Source of Christian Mystery begins by showing the unity between Christian thought (theology) and Christian living (spirituality). Then Balthasar turns to the specializations and divisions of theology, and shows how the unity of dogma governs and directs the specializations. Next, he examines "the dreadful multiplicity of churches and its pseudo-justfication through the alleged variety of theologies" in the New Testament". Finally, Balthasar has the reader focus on himself, challenging him to consider where "the integrated simplicity of his own existence might lie".

Balthasar argues against an imprudent simplification of theology which seeks to return to the "simplicity" of ancient Christian thought by throwing away allegedly useless accretions. "It is thought," says Balthasar in the Foreword, "that liberating unity is achieved by ridding oneself of superfluous amassed goods." One cannot remain true to theology, argues Balthasar, by throwing parts of the tradition overboard in an attempt to find a lost, longed-for theological unity. A prior experience of the unity of theology is required to make sound judgments about what is useless and what is helpful.