Pope St Pius X promulgated his encyclical Pascendi Dominici Gregis on 8 September 1907, the festival of Our Lady’s nativity. Thus, he places the whole controversy about the heresy of modernism under the gaze of the Immaculate One, who is always interceding for the Church.
Whatever may have been the encyclical’s reception at the time, it is clear to the honest eye that Pascendi cannot be considered a mere doctrinal antique, an artifact of bygone ecclesial intolerance. Today, the effects of this synthesis of all heresies are to be met with everywhere. In a word, theological modernists are those who have no time for the truly supernatural. Divine Revelation, grace, sacred scripture and sacred tradition, liturgy, the Church herself—all these are displaced and entirely subjected to anthropocentric concerns.
Again, we have the sad advantage of being able to mark what happened to Catholic theology, worship, and culture in the mid twentieth century. The errors of St Pius X’s time have borne their fruit in our own.
As for Our Lady, the saintly pope names her cuntarum hæresum interemptrix, the destroyer of all heresies. Does he have precedent for doing so? He does. We find an antiphon in the Roman Breviary which reads, ‘Rejoice, Virgin Mary! You alone have brought to ruin all the heresies throughout the world.’ We ought to think of the conflict between St Cyril and Nestorius and the resulting orthodox Marian victory at Ephesus.
Here, our purpose is to acknowledge how the sacred liturgy joins together the defeat of theological error and joy. Rightly indeed is Our Lady exhorted to rejoice, for joy only flourishes with the truth.
The point is further proved for us: the psalm to which this antiphon is attached is the 95th.—
Sing to the Lord a new song: sing to the Lord, all the earth . . . For he shall judge the world in equity, and the people in his truth.
When we study the entire psalm, we see that the modernist could never pray it, because it is precisely the opposite of his joyless doctrine. Modernism pretends to the glorification of man, but has nothing in common with the vigorous simplicity of Psalm 95.
In the end, all the mysteries of Mary point to the boundlessness of God’s ingenuity to save. Which is the very thing that the modernists refuse to see. This is why, in the language of the liturgy, she alone is the destroyer of all heresies. Christ is the Savior, and this Savior has a mother. Who more than she is concerned with right understanding of his identity? On the contrary, how entirely foreign to the Catholic thing are the mitigations and insinuations of the modernists!
Rejoice, indeed. And Pope St Pius X knew it: our Lady reminds the Church that joy is true only when it is also faithful.
 Pascendi, 59: ‘adsit prece atque auxilio Virgo immaculata, cunctarum haeresum interemptrix.’
 Common of Feasts of the Blessed Virgin Mary, Matins, third nocturne: Gaude, Maria Virgo: cunctas hæreses sola interemisti in universo mundo.
 Cf 1 Corinthians 13, 6.