I’m curious, what does the Church have to say about “sola gratia”–grace alone?
The church totaly agrees with this.
As always, our first recourse ought to be the Catechism:
1987 The grace of the Holy Spirit has the power to justify us, that is, to cleanse us from our sins and to communicate to us “the righteousness of God through faith in Jesus Christ” and through Baptism:34
But if we have died with Christ, we believe that we shall also live with him. For we know that Christ being raised from the dead will never die again; death no longer has dominion over him. The death he died he died to sin, once for all, but the life he lives he lives to God. So you also must consider yourselves as dead to sin and alive to God in Christ Jesus.35
1988 Through the power of the Holy Spirit we take part in Christ’s Passion by dying to sin, and in his Resurrection by being born to a new life; we are members of his Body which is the Church, branches grafted onto the vine which is himself:36
[God] gave himself to us through his Spirit. By the participation of the Spirit, we become communicants in the divine nature. . . . For this reason, those in whom the Spirit dwells are divinized.37
1989 The first work of the grace of the Holy Spirit is conversion, effecting justification in accordance with Jesus’ proclamation at the beginning of the Gospel: "Repent, for the kingdom of heaven is at hand."38 Moved by grace, man turns toward God and away from sin, thus accepting forgiveness and righteousness from on high. "Justification is not only the remission of sins, but also the sanctification and renewal of the interior man.39
1990 Justification detaches man from sin which contradicts the love of God, and purifies his heart of sin. Justification follows upon God’s merciful initiative of offering forgiveness. It reconciles man with God. It frees from the enslavement to sin, and it heals.
1991 Justification is at the same time the acceptance of God’s righteousness through faith in Jesus Christ. Righteousness (or “justice”) here means the rectitude of divine love. With justification, faith, hope, and charity are poured into our hearts, and obedience to the divine will is granted us.
1992 Justification has been merited for us by the Passion of Christ who offered himself on the cross as a living victim, holy and pleasing to God, and whose blood has become the instrument of atonement for the sins of all men. Justification is conferred in Baptism, the sacrament of faith. It conforms us to the righteousness of God, who makes us inwardly just by the power of his mercy. Its purpose is the glory of God and of Christ, and the gift of eternal life:40
But now the righteousness of God has been manifested apart from law, although the law and the prophets bear witness to it, the righteousness of God through faith in Jesus Christ for all who believe. For there is no distinction: since all have sinned and fall short of the glory of God, they are justified by his grace as a gift, through the redemption which is in Christ Jesus, whom God put forward as an expiation by his blood, to be received by faith. This was to show God’s righteousness, because in his divine forbearance he had passed over former sins; it was to prove at the present time that he himself is righteous and that he justifies him who has faith in Jesus.41
1993 Justification establishes cooperation between God’s grace and man’s freedom. On man’s part it is expressed by the assent of faith to the Word of God, which invites him to conversion, and in the cooperation of charity with the prompting of the Holy Spirit who precedes and preserves his assent:
When God touches man’s heart through the illumination of the Holy Spirit, man himself is not inactive while receiving that inspiration, since he could reject it; and yet, without God’s grace, he cannot by his own free will move himself toward justice in God’s sight.42
1994 Justification is the most excellent work of God’s love made manifest in Christ Jesus and granted by the Holy Spirit. It is the opinion of St. Augustine that “the justification of the wicked is a greater work than the creation of heaven and earth,” because "heaven and earth will pass away but the salvation and justification of the elect . . . will not pass away."43 He holds also that the justification of sinners surpasses the creation of the angels in justice, in that it bears witness to a greater mercy.
1995 The Holy Spirit is the master of the interior life. By giving birth to the "inner man,"44 justification entails the sanctification of his whole being:
Just as you once yielded your members to impurity and to greater and greater iniquity, so now yield your members to righteousness for sanctification. . . . But now that you have been set free from sin and have become slaves of God, the return you get is sanctification and its end, eternal life.45
1996 Our justification comes from the grace of God. Grace is favor, the free and undeserved help that God gives us to respond to his call to become children of God, adoptive sons, partakers of the divine nature and of eternal life.46
1997 Grace is a participation in the life of God. It introduces us into the intimacy of Trinitarian life: by Baptism the Christian participates in the grace of Christ, the Head of his Body. As an “adopted son” he can henceforth call God “Father,” in union with the only Son. He receives the life of the Spirit who breathes charity into him and who forms the Church.
1998 This vocation to eternal life is supernatural. It depends entirely on God’s gratuitous initiative, for he alone can reveal and give himself. It surpasses the power of human intellect and will, as that of every other creature.47
1999 The grace of Christ is the gratuitous gift that God makes to us of his own life, infused by the Holy Spirit into our soul to heal it of sin and to sanctify it. It is the sanctifying or deifying grace received in Baptism. It is in us the source of the work of sanctification:48
Therefore if any one is in Christ, he is a new creation; the old has passed away, behold, the new has come. All this is from God, who through Christ reconciled us to himself.49
2000 Sanctifying grace is an habitual gift, a stable and supernatural disposition that perfects the soul itself to enable it to live with God, to act by his love. Habitual grace, the permanent disposition to live and act in keeping with God’s call, is distinguished from actual graces which refer to God’s interventions, whether at the beginning of conversion or in the course of the work of sanctification.
2001 The preparation of man for the reception of grace is already a work of grace. This latter is needed to arouse and sustain our collaboration in justification through faith, and in sanctification through charity. God brings to completion in us what he has begun, "since he who completes his work by cooperating with our will began by working so that we might will it:"50
Indeed we also work, but we are only collaborating with God who works, for his mercy has gone before us. It has gone before us so that we may be healed, and follows us so that once healed, we may be given life; it goes before us so that we may be called, and follows us so that we may be glorified; it goes before us so that we may live devoutly, and follows us so that we may always live with God: for without him we can do nothing.51
2002 God’s free initiative demands man’s free response, for God has created man in his image by conferring on him, along with freedom, the power to know him and love him. The soul only enters freely into the communion of love. God immediately touches and directly moves the heart of man. He has placed in man a longing for truth and goodness that only he can satisfy. The promises of “eternal life” respond, beyond all hope, to this desire:
If at the end of your very good works . . ., you rested on the seventh day, it was to foretell by the voice of your book that at the end of our works, which are indeed “very good” since you have given them to us, we shall also rest in you on the sabbath of eternal life.52
2003 Grace is first and foremost the gift of the Spirit who justifies and sanctifies us. But grace also includes the gifts that the Spirit grants us to associate us with his work, to enable us to collaborate in the salvation of others and in the growth of the Body of Christ, the Church. There are sacramental graces, gifts proper to the different sacraments. There are furthermore special graces, also called charisms after the Greek term used by St. Paul and meaning “favor,” “gratuitous gift,” "benefit."53 Whatever their character - sometimes it is extraordinary, such as the gift of miracles or of tongues - charisms are oriented toward sanctifying grace and are intended for the common good of the Church. They are at the service of charity which builds up the Church.54
2004 Among the special graces ought to be mentioned the graces of state that accompany the exercise of the responsibilities of the Christian life and of the ministries within the Church:
Having gifts that differ according to the grace given to us, let us use them: if prophecy, in proportion to our faith; if service, in our serving; he who teaches, in his teaching; he who exhorts, in his exhortation; he who contributes, in liberality; he who gives aid, with zeal; he who does acts of mercy, with cheerfulness.55
2005 Since it belongs to the supernatural order, grace escapes our experience and cannot be known except by faith. We cannot therefore rely on our feelings or our works to conclude that we are justified and saved.56 However, according to the Lord’s words "Thus you will know them by their fruits"57 - reflection on God’s blessings in our life and in the lives of the saints offers us a guarantee that grace is at work in us and spurs us on to an ever greater faith and an attitude of trustful poverty.
A pleasing illustration of this attitude is found in the reply of St. Joan of Arc to a question posed as a trap by her ecclesiastical judges: "Asked if she knew that she was in God’s grace, she replied: ‘If I am not, may it please God to put me in it; if I am, may it please God to keep me there.’"58
So to sum up the Catechism excerpts posted above, Man is saved through the grace of God alone.
The real question is what we do with the grace we’ve been given—the sacraments are what help us do what we ought to do.