In his Treatise of True Devotion to the Blessed Virgin, St. Grignon de Montfort has distinguished a number of different degrees of true devotion to the Mother of God. He speaks only briefly of the forms of false devotion ---- that which is altogether exterior, or presumptuous, or inconstant, or hypocritical, or self-interested ---- since his main concern is true devotion.
Like the other Christian virtues, true devotion grows in us with charity, advancing from the stage of the beginner to that of the more proficient, and continuing up to the stage of the perfect. The first degree or stage is to pray devoutly to Mary from time to time, for example, by saying the Angelus when the bell rings. The second degree is one of more perfect sentiments of veneration, confidence and love; it may manifest itself by the daily recitation of the Rosary ---- five decades or all fifteen. fu the third degree, the soul gives itself fully to Our Lady by an act of consecration so as to belong altogether to Jesus through her. 
What does this Consecration mean?
This act of consecration consists in promising Mary to have constant filial recourse to her and to live in habitual dependence on her, so as to attain to more intimate union with Our Blessed Lord and through Him with the Blessed Trinity present in our souls. The reason for making it lies. St. Grignon de Montfort says, in the fact that God has willed to make use of Mary for the sanctification of souls, having already made use of her to bring about the Incarnation (Treatise on True Devotion, ch. I, a. I, no. 44).
The Saint continues: 'I do not think that anyone can attain to great union with Our Blessed Lord or perfect fidelity to the Holy Ghost without being closely united to Our Lady and depending very much on her help . . . She was full of grace when she was saluted by the Archangel Gabriel, she was superabundantly filled with grace by the Holy Ghost when He overshadowed her, she so advanced in grace from day to day and from moment to moment as to arrive at an inconceivable summit of grace; on which account the Most High has made her His unique treasurer and the unique dispenser of His graces, so that she may ennoble, enrich and elevate whom she wills, and make whom she wills enter the narrow gate of Heaven . . . Jesus is everywhere and always the Son and the fruit of Mary; Mary is everywhere the true tree which bears the fruit of life and the true mother who produces it.'
In the same chapter, a little earlier, we read: 'We may apply to Mary with even more truth than St Paul applies them to himself the words: "My little children, of whom I am in labor again, until Christ be formed in you. I am in labor daily with God's children till Jesus be formed in them in the fulness of His age." St. Augustine says that the predestined are in this world hidden in the womb of Mary in order to become conformed to the image of the Son of God; and there she guards, nourishes, and supports them and brings them forth to glory after death, which is the true day of their birth ---- the term by which the Church always speaks of the death of the just. O mystery of grace unknown to the reprobate and little understood by the predestined!' Mary is truly the mother of the just, conceiving them spiritually and bringing them forth after death by their entry into glory, which is their defmitive spiritual birth. It is clear then that it would be a falling short in humility to neglect to have frequent recourse to the Universal Mediatrix whom Divine Providence has given us as our true spiritual mother to form Christ in us. It is clear also that theology cannot but recognise that it is lawful and more than lawful to consecrate oneself to Mary, Mother and Queen of all men. 
Consecration to Our Lady is a practical form of recognition ofher universal mediation and a guarantee ofher special protection. It helps us to have continual childlike recourse to her and to contemplate and imitate her virtues and her perfect union with Christ. In the practice of this complete dependence on Mary, there may be included ---- and St. Grignon de Montfort invites us to it ---- the resignation into Mary's hands of everything in our good works that is communicable to other souls, so that she may make use of it in accordance with the will of her Divine Son and for His glory. 'I choose thee this day, O Mary, in the presence of the whole court of Heaven, as my Mother and Queen. I give and consecrate to you as your slave my body and my soul, my interior and exterior possessions, and even the value of my past, present and future good actions, allowing you the full right to dispose of me and of all that belongs to me, without any exception whatever, according to your good pleasure, for the greater glory of God, in time and in eternity.' This offering is really the practice of the so-called heroic act, there being question here not of a vow but of a promise made to the Blessed Virgin. 
We are recommended to offer our exterior possessions to Mary, that she may preserve us from inordinate attachment to the things of this world and inspire us to make better use of them. It is good also to consecrate to her our bodies and our senses that she may keep them pure.
The act of consecration gives over to Mary also our soui and its faculties, our spiritual possessions, virtues and merits, all our good works past, present and future. It is necessary, however, to explain how this can be done. Theology gives us the answer by distinguishing what is communicable to others in our good works from what is incommunicable.
To begin at the other end of the problem, our merits de condigno which constitute a right in justice to an increase of grace and to eternal glory are incommunicable. Our merits de condigno differ in that from those of Our Blessed Lord. He was Head of the human race and could in justice communicate His merits to us. If, therefore, we offer our merits de condigno to Mary, it is not in order that she may give them to others but that she may keep them for us, that she may help us to make them bear fruit, and, if we have the misfortune to lose them by mortal sin, that she may obtain for us the grace of really fervent contrition.
There is, however, something in our good works which we can communicate to others whether on earth or in purgatory.  There is in the first place the merit de congruo proprie, founded on the rights of friendship with God by grace. God gives grace to some because of the good intentions and good works of others who are His friends. There are, in the second place, our prayers; we can and should pray for our neighbor, for his conversion and his spiritual progress; we should pray also for the dying, for the Souls in Purgatory.
There are finally our acts of satisfaction. We can make satisfaction de congruo for others, for example, by accepting our daily crosses to help to expiate for their sins. We may even, if God moves us to do so by His grace, accept the penalty due to their sins as Mary did at the foot of the Cross, and thereby draw down the Divine Mercy on them.  This the Saints did frequently. An example is found in the life of St. Catherine of Siena. To a young Sienese whose heart was full of hate of his political enemies she said: 'Peter, I take on myself all your sins, I shall do penance in your place; but do me one favour; confess your sins.' 'I have been frequently to Confession,' answered Peter. 'That is not true,' replied the Saint. 'It is seven years since you were at Confession,' and she proceeded to enumerate an the sins of his life. Confounded, he repented and pardoned his enemies. Even without having all St. Catherine's generosity, we can accept our daily crosses to help other souls to pay the debt they owe to the Divine justice.
We can also gain indulgences for the souls in Purgatory, opening to them the treasury of the merits and satisfactions of Christ and the saints and hastening the day of their liberation.
There are, therefore, three things which we can share with others: our merits de congruo, our prayers, our satisfaction. And if we put these in Mary's hands for others, we ought not to be surprised if she sends us crosses ---- proportionate, of course, to our strength ---- to make us really work for the salvation of souls.
Who are those who may be advised to make this act of consecration? It certainly should not be recommended to people who would make it for merely sentimental reasons or through spiritual pride, and would not understand its true meaning. But those who are truly spiritual may be recommended to make it for a few days at first and then for some longer time; when finally they are prepared they may make it for their whole lives.
Someone may say that to give everything to Our Lady is to strip oneself, to leave one's own debts unpaid, and so to add to one's term in Purgatory. This is in fact the difficulty the devil suggested to St. Brigid of Sweden when she thought of making the act of donation to Mary. Our Blessed Lord explained, however, to the Saint that the objection sprang from self-love and made no allowance for Mary's goodness. Mary will not be outdone in generosity: her help to us will far exceed what we give her. The very act of love which prompts our donation will itself obtain remission of part of our Purgatory.
Others wonder if making the act of donation to Mary leaves them free to pray for relatives and friends afterwards. They forget that Mary knows the obligations of charity better than we do: she would be the first to remind us of them. There may even be some among our relatives and friends on earth and in Purgatory who have urgent need of prayers and satisfactions, without our knowing who they are. Mary, however, knows who they are, and she can help them out of our good works if we have put them at her disposal.
Thus understood, consecration and donation make us enter more fully, under Mary's guidance, into the mystery of the Communion of Saints. It is a perfect renewal of the baptismal promises. 
Fruits of this Consecration
'This devotion,' St. Grignon de Montfort tells us,  'gives us up altogether to the service of God, and makes us imitate the example of Our Blessed Lord, Who willed to be "subject" in regard to His Blessed Mother (Luke ii, 51). It obtains for us the special protection of Mary, who purifies our good works and adorns them when she offers them to her Divine Son. It leads us to union with Our Blessed Lord; it is an easy, short, perfect and safe way. It confers great interior freedom, procures great benefits for our neighbor, and is an excellent means of assuring our perseverance.' The Saint develops each of these points in a most practical way.
He speaks of the easiness of the way in ch. 5, a. 5: 'It is an easy way, one followed and prepared for us by Our Blessed Lord in His own coming, one where there are no obstacles in reaching Him. It is true that one can arrive at union with God by following other roads; but there will be many more crosses and trials, and many more difficulties which it will not be easy to surmount ---- there will be combats and strange agonies, steep mountains, sharp thorns, fearful deserts. But the way of Mary is sweeter and more peaceful.
'Even along the way of Mary there are stern battles and great difficulties; but our good Mother makes herself so near and present to her faithful servants to enlighten them in their doubts, to strengthen them in their fears, and to sustain them in their battles, that in truth the Virgin's way to Jesus is a way of roses and honey compared with all others.' The Saint adds that the truth of this can be seen from the lives of the Saints who have followed this way most particularly: St. Ephrem, St. John Damascene, St. Bernard, St. Bonaventure, St. Bernardine of Siena, St. Francis de Sales.
A little further on in the same chapter, the Saint states that Mary's servants 'receive from her Heaven's greatest graces and favors which are crosses; but it is the servants of Mary who bear the crosses with most ease, merit and glory; and what would hold back another makes them advance,' for they are more aided by the Mother of God, who obtains for them the unction oflove in their trials. It is wonderful how Mary makes the cross at the same time easier to bear and more meritorious: easier to bear because she helps us, and more meritorious because she obtains for us greater charity, which is the principle of greater merit.
'It is a short way . . . one advances more in a little while of submission to and dependence on Mary than in many years of self-will and self-reliance . . . We can advance with giant strides along the path by which Jesus came to us. . . In a few years we shall arrive at the fulness of the perfect age.' 
'It is a perfect way, chosen by God Himself . . . The Most High descended to us by way of the humble Mary without losing anything of His Divinity; it is by Mary that little ones can rise perfectly and divinely to the Most High without fear.'
It is finally a safe way, for the Blessed Virgin preserves us from the illusions of the devil and our imagination. she preserves us from sentiment as well, calming and ruling our sensibility, giving it a pure and holy object, and subordinating it to the rule of the will vivified by charity.
In consecration to Mary, we fmd great interior liberty: this is the reward of putting ourselves in such complete dependence on Mary. Scruples are banished; the heart dilates with confidence and love. The saint confirms this point by referring to what he read in the life of the Dominican, Mother Agnes de Langeac, 'who, suffering great anguish of soul, heard a voice which said to her that if she wished to be delivered and to be protected from her enemies, she should make herself at once the slave of Jesus and His Holy Mother . . . When she had done so all her anguish and scruples ceased, and she found herself in a state of great peace, as a result of which she determined to teach the devotion to others . . . among whom was M. Olier, the founder of the seminary of Saint-Sulpice, and many other priests of the same seminary.' It was in the same seminary that St. Grignon de Montfort received his priestly formation.
'Finally, this devotion is one which procures the good of our neighbor and it is for those who live by it an admirable means of persevering in grace . . . for by it one gives to Mary, who is faithful, all that one has . . . It is on her fidelity that reliance is placed . . . that she may preserve and increase our merits in spite of all that could make us lose them . . . Do not commit the gold of your charity, the silver of your purity, the waters of heavenly graces, or the wine of your merits and virtues . . . to broken vessels such as you yourselves are; else you will be despoiled by robbers, that is by the demons, who watch day and night for a favorable opportunity Put all your treasures, all your graces and virtues, in the womb and in the heart of Mary: she is a spiritual vessel, a vessel of honor, a singular vessel of devotion.
'Souls who are not born of blood nor of the will of the flesh nor of the will of man, but of God and of Mary, understand and relish what I say; and it is for them that I write . . . If a soul gives itself to Mary without reserve, she gives herself to it without reserve' and helps it to find the road which leads to the eternal goal.
Such are the fruits of this consecration: Mary loves those who commit themselves to her fully; she guides, directs, defends, protects, supports and intercedes for them. It is good to offer ourselves to her so that she may offer us to her Son according to the fulness of her prudence and her zeal.
There are also fruits of a higher order which this devotion produces, fruits which are strictly mystical, as we shall explain in the next section. 
why St. Grignon de Montfort speaks in his formula of 'Consecration of
to Jesus by the hands of Mary'. In the course of his treatise he
says it more briefly, 'Consecration to Mary,' meaning thereby
to Jesus through her.
The expression 'holy slavery' used by the Saint has been sometimes criticised. This is to forget that it is a slavery of love which accentuates rather than diminishes the filial character of our love of Mary. Besides, as Mgr. Garnier, Bishop of Luçon, remarked in a pastoral letter of March 11th, 1922, if there are in the world slaves ofhuman respect, of ambition, of money, and of shameful passions, there are also, thank God, slaves of conscience and of duty. The holy slavery belongs to this group. The expression 'holy slavery' is a striking metaphor, opposed to the slavery of sin.
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