As noted in yesterday’s post, St. Thomas Aquinas’s thought played a role in my conversion, primarily through the works of the great Thomists, Jacques & Raissa Maritain, whose book Liturgy & Contemplation moved me deeply prior to my wife and I being baptized.
This marvelous book is also available online.
The chapter entitled “Contemplation & the call to perfection” was a key element, and it is posted here
"Contemplation and the call to perfection
"Dominating the whole spiritual life is the call to perfection.
"Be you therefore perfect, as also your heavenly Father is perfect."
"Christian perfection consists essentially in charity," says Saint Thomas [Aquinas]. "Indeed a thing is said to be perfect in so far as it attains its proper end—the proper end of a thing being its ultimate perfection. Now it is charity that unites us to God, Who is the last end of the human soul: he that abideth in charity, abideth in God, and God in him."
"It follows that perfection falls under the divine precept, because it is on charity, on the twofold love of God and neighbor, that the two precepts of the divine Law bear.
"And "the love of God and of neighbor does not fall under the precept according to a certain measure only . . . as is evident from the very form of the precept, which implies perfection and totality: 'Thou shalt love the Lord thy God with thy whole heart, thy whole soul, thy whole mind, thy whole strength, and thy neighbor as thyself.' This is why the Apostle says (I Tim., 1): the end of the commandment is charity. Now the end does not admit of measure—measure applies only to means.
“According to Saint Bernard's saying, the measure of loving God is to love Him without measure—"modus diligendi, sine modo diligere."
"Estote perfecti." "Thus the Lord in His goodness," says Saint Benedict, commenting on this word of Christ's in the prologue to his Rule, "shows us the way of life"—the way of eternal life, which must never be interrupted, so that charity may grow unceasingly, at the same time as humility which is the dawn of beatitude—"incipit beatitudo ab humilitate."
“The way of life which Christ shows us is a way in which one advances towards God and towards the Beatific Vision with steps of living faith, of hope, and of love. And because it makes one advance towards perfection, this way itself is perfect.
“Perfection is not a mathematical point. It is a life in state of growth; there are degrees in perfection. What is prescribed by the precept is to tend to perfection as to an end, and when one has begun to make his way towards it he is already accomplishing the precept; and one begins to make his way towards it as soon as he has charity. It is in this sense that Saint Thomas [Aquinas] tells us: "Since what falls under the precept can be accomplished in diverse ways, one does not sin against the precept by the fact alone that he does not fulfill it in the best way; it suffices, for the precept not to be transgressed, that it be accomplished in one way or another. "And Cajetan writes: "The perfection of charity is commanded as an end; and we must wish to attain the end, the whole end. But precisely because it is an end, it suffices, for a man not to transgress the precept, that he be in the state of attaining this perfection one day, even if in eternity. Whoever possesses charity, even in the feeblest degree, and is thus advancing towards Heaven, is in the way of perfect charity, and consequently avoids the transgression of the precept...."
“It is only in Heaven where the soul sees God face to face that the precept is accomplished in an entirely perfect way. But there is a perfection of charity compatible with the present life, a perfection in state of growth; it implies "the exclusion of all things which are repugnant to the movement of love towards God"—the exclusion not only of mortal sin, but also of "all that hinders the affection of the soul from tending entirely towards God." And thus, whatever may be the vocation of each, the saying of Saint John of the Cross concerns us all: "In the evening of this life you will be judged according to your love."
“Let us recall now that contemplation, as Father Lallemant puts it, "proceeds from love and tends to love," that it is "the use of the purest and most perfect charity," and that love is "its source, its exercise and its end"—as indeed Saint Paul affirmed, for whom charity—in the words of Father Lebreton—which "at death will flower into eternal life," is "the way and the end of contemplation." And let us recall too that according to the teaching of Saint Thomas [Aquinas] contemplation "relates directly and immediately to the love of God Himself," and that it "is ordered not to any love of God whatever, but to perfect love." What are we to conclude from all this if not that the precept of perfection protects, so to speak, and sanctions the desire for contemplation: there is no true contemplation without progress towards perfection; and on the other hand there is nothing which accelerates better than contemplation one's progress towards perfection and the accomplishment in us of the desire for perfection.”
Maritain, Jacques & Raissa. (1960) Liturgy & Contemplation . Geoffrey Chapman: London. (pp.40-44)