In virtue of the Apostolic Letter Exulta Lusitania felix; O felix Padua gaude [Jan. 16, 1946], Pope Pius XII, solemnly declared St. Anthony of Padua [1196-1231] a Doctor of the Church Universal. St. Anthony, the new Doctor Evangelicus, thus becomes the twenty-ninth Saint to be elevated to this high rank and the second of the Franciscan Order to enjoy this privilege, the other being the "Seraphic Doctor," St. Bonaventure of Bagnoreggio [1221-74].
Whereas all knew, I dare say, that St. Anthony was a most popular Saint, a wonderful preacher, and a great thaumaturgist, few looked upon him as a deep theologian or a learned teacher. True, he wrote no Summa as did St. Thomas of Aquin, nor a Commentary on the Sentences of Peter of Lombardy, as did most medieval scholastics; but he did bequeath to posterity his sermons,  a veritable font of theology and doctrine, so much so that the Holy Father in the above-quoted Apostolic Letter could truly say:
In this article I hope to give a brief analysis of the beautiful sermon of the new Doctor of the Church on the Assumption of the Blessed Virgin Mary. Rev. Diomede Scaramuzzi, O.F.M., recently compiled from the sermons of St. Anthony a whole Summa theologica, as it were, of the Saint, in a work entitled La Figura lntellettuale di San Antonio di Padova alla luce della critica,  which was considered of such importance that the Sacred Congregation of Rites included it in the official Acta of its Process for the Informatio, Inquisitio, and Confirmatio of the title of Doctor of the Church to be bestowed on our Saint.  It is on Scaramuzzi's learned studies and on the publication of St. Anthony's authentic sermons by that ardent lover of Antoniana, Very Rev. Antonio M. Locatelli,  Canon of the Cathedral of Padua [+1902], that I base the following expose of the sermon.
During the early Middle Ages the doctrine of the Assumption of Our Lady was not admitted by all, nor was the feast-day universally celebrated throughout the Church;  the important Usuard Martyrology, written by a Benedectine monk of the Abbey of St. Germain-des-Pres [Paris] shortly before 875, actually denied it.  However, since the days of St. John Damascene [675-749] both the belief in the doctrine and the celebration of the feast, although on various days,  had so increased from century to century that by the beginning of the 13th Century it was the common doctrine of theologians. There is a legend current that St. Anthony also for a time doubted the Assumption of the Blessed Virgin Mary, but, as the result of a vision, he became one of its most ardent defenders.  The Franciscan school in general, including St. Bonaventure,  defended the doctrine. So did the Thomistic school, following its illustrious founder.  Thus on this phase, at least, of Mary's prerogatives, there was unanimity of opinion.
St. Anthony's sermon on the Assumption [In Assumptione S. Mariae Virginis] is published by Locatelli  and by P. Antonio M. Josa, O.F.M. Conv., the former Prefect of the Biblotheca Antoniana at Padua, in his Sermones S. Antonii de Padua in laudem gloriosae Virginis Mariae.  Since there are no direct and formal texts in the Sacred Scriptures on the corporeal assumption of the Blessed Virgin Mary, St. Anthony bases his defense of the doctrine on accommodated texts which he confirms by arguments of convenience [argumenta convenientiae] and by theological inductions and deductions [rationes theologicae].
Commenting on the text of Isaias [60: 13], "Et locum pedum tuorum glorificabo," ["And I will glorify the place of Thy feet."] the Evangelical Doctor says: "The place of the feet of Our Lord was the Blessed Virgin Mary from whom He assumed humanity and whom today He glorified because He exalted Her above the choirs of Angels." In this text, continues our Saint, "it evidently follows that the Blessed Virgin Mary, who was the resting place of the feet of the Lord, was glorified because She was taken up into Heaven."
Explaining the text in Psalm [131: 8], "Ex surge, Domine, in requiem tuam, tu et arca sanctificationis tuae," ["Arise, O Lord into Thy resting place: Thou and the Ark, which Thou hast sactified. "] St. Anthony says that the first part of this verse refers to Christ's Resurrection and Ascension, the second part to the "ark which Thou hast sanctified," i.e. to Christ's Blessed Mother, whom He took up to Himself into Heaven: "cum in hac die [Aug. 15] ad aeternum thalamum est assumpta."
Continuing with the thought of the "ark which the Lord had sanctified," [Ps. 131: 8] St. Anthony compares Mary with the ark of Noah which after the flood finally rested on Mt. Ararat in the mountains of Armenia, i.e. "super choros angelorum," because in Her Assumption She "was placed above the choirs of Angels."
He also compares Mary to Esther and says that, like Her type in the Old Testament, Mary too was led to the room of a king: "ducta est ad cubiculum Regis," [Esther, 2: 15-17] "to the ethereal dwelling, in which the King of kings, the joy of the Angels, sits upon a starry throne, Jesus Christ, Who loved the same glorious Virgin above all other women, because of Her He assumed flesh."  How like the antiphons of the Roman Breviary for the Feast of the Assumption!
Then, in admiration of the dignity accorded Mary, led to the throne room of the King and exalted above all the choirs of Angels, St. Anthony breaks forth into the following exclamation: "O inaestimabilis Mariae dignitas! O inenarrabilis gratiae sublimitas! O investigabilis misericordiae profunditas!" It was on account of Mary's Divine maternity that She was taken up into Heaven and crowned: "et ideo hodie coronari meruit." In other words, the ratio theologica of Mary's Assumption into Heaven and coronation as Queen of the Angels is Her Divine maternity. Herein lies real theological progress. As Mary's Immaculate Conception  was preparatory to Her maternity the greatest of Her prerogatives, so was Her Assumption into Heaven the crowning glory of both. Because She had been immaculately conceived it behooved Almighty God [conveniens erat] to preserve Her body from corporeal corruption. On the other hand, because it was from Mary's chaste body that the Son of God assumed flesh and blood, it behooved God to preserve Her body as free from material, corporeal corruption as He did the body of His Son through the latter's Resurrection and Ascension.
Commenting on the Introit and the Gospel of the day: "Introivit Jesus in quoddam castellum" Anthony says: "The castle into which Jesus entered at the moment of His Incarnation was Mary, His virginal Mother:" "Castellum enim est Beata Maria, quae quia totius castitatis claritate nituit, ideo in ipsam. Dominus intravit." Then, playing on the Gospel narrative in his own inimitable analogical and symbolical method of Scriptural interpretation, he continues: "Around every castle is a wall and on every wall a tower. The wall which protected Mary was Her virginity; the tower defending the castle, Her humility." The tower was straight and long ["turris dicta est 'teres,' idest directa, et longa"]. It was straight because She looked up solely to Him, Who regarded Her humility; long, because in the word of humility "Behold the handmaid of the Lord" She became the Queen of Heaven.
Finally, accommodating the Gospel text of the Feast of the Assumption referring to Martha and Mary, the sisters of Lazarus, St. Anthony says: "Our Mary, the Mother of Christ, was both a Martha and a Mary. She was a Martha because She wrapped up the Child in swaddling clothes, laid Him in a manger, nursed Him from a breast full of heavenly nourishment, fled with Him into Egypt and returned with Him therefrom." But She was also a Mary, because, like the other sister of Lazarus, sitting at the feet of Jesus "She kept all these things in Her heart."
En passant, this sermon on the Assumption is an excellent example of the homiletic method used by St. Anthony: the combination of a homily on the Gospel, the epistle, the Introit of the Mass, and the history of the Old and New Testaments as expounded by the Fathers in the second nocturn of the Divine office. This fourfold application St. Anthony calls the "four wheels of the chariot of Elias" [quatuor rotae quadrigae Eliae] which carried the prophet up to Heaven. 
Taken from In Praise of Our Blessed Mother, a collection of Marian articles from the American Ecclesiastical Review, 1952.