A good habit of the mind or will, supernaturally infused into the soul, whose immediate object is God.
(Modern Catholic Dictionary)
The theological virtues are the foundation of Christian moral activity; they animate it and give it its special character. They inform and give life to all the moral virtues. They are infused by God into souls of the faithful to make them capable of acting as His children and of meriting eternal life. They are the pledge of the presence and action of the Holy Spirit in the faculties of the human being. (CCC 1813)
Faith---the theological virtue in which we believe in God and believe all that He has said and revealed to us, and that the Holy Church proposes for our belief, because He is Truth itself. By faith 'man freely commits his entire self to God.' (DV 5). For this reason the believer seeks to know and do God's will. 'The righteous shall live by faith.' Living faith 'work[s] through charity.' (Rom 1:17; Gal 5:6)
The gift of faith remains in one who has not sinned against it. (Cf. Council of Trent (1547): DS 1545). But 'faith apart from works is dead' (Jas 2:26): when it is deprived of hope and love, faith does not fully unite the believer to Christ and does not make him a living member of His body.
The disciple of Christ must not only keep the faith and live on it, but also profess it, confidently bear witness to it, and spread it: 'All however must be prepared to confess Christ before men and to follow Him along the way of the Cross, amidst the persecutions which the Church never lacks.' (LG 42; cf. DH 14). Service of and witness to the faith are necessary for salvation: 'So every one who acknowledges Me before men, I also will acknowledge before My Father who is in heaven; but whoever denies Me before men, I also will deny before My Father who is in heaven.' (CCC 1814-1816)
Hope--- Hope is the theological virtue by which we desire the kingdom of heaven and eternal life as our happiness, placing our trust in Christ's promises and relying not on our own strength, but on the help of the grace of the Holy Spirit. 'Let us hold fast the confession of our hope without wavering, for He who promised is faithful.' (Heb 10:23) 'The Holy Spirit... He poured out upon us richly through Jesus Christ our Saviour, so that we might be justified by His grace and become heirs in hope of eternal life.' (Titus 3:6-7)
The virtue of hope responds to the aspiration to happiness which God has placed in the heart of every man; it takes up the hopes that inspire men's activities and purifies them so as to order them to the Kingdom of heaven; it keeps man from discouragement; it sustains him during times of abandonment; it opens up his heart in expectation of eternal beatitude. Buoyed up by hope, he is preserved from selfishness and led to the happiness that flows from charity.
Christian hope takes up and fulfills the hope of the chosen people which has its origin and model in the hope of Abraham, who was blessed abundantly by the promises of God fulfilled in Isaac, and who was purified by the test of the sacrifice. (Cf. Gen 17:4-8; 22:1-18). 'Hoping against hope, he believed, and thus became the father of many nations.' (Rom 4:18)
Christian hope unfolds from the beginning of Jesus' preaching in the proclamation of the beatitudes. The beatitudes raise our hope towards heaven as the new promised land; they trace the path that leads through the trials that await the disciples of Jesus. But through the merits of Jesus Christ and His Passion, God keeps us in the 'hope that does not disappoint.' (Rom 5:5) Hope is the 'sure and steadfast anchor of the soul...that enters...where Jesus has gone as a forerunner on our behalf.' (Heb 6:19-20) Hope is also a weapon that protects us in the struggle for salvation: 'Let us ...put on the breastplate of faith and charity, and for a helmet the hope of salvation.' (1 Thess 5:8) It affords us joy even under trial: 'Rejoice in your hope, be patient in tribulation.' (Rom 12:12) Hope is expressed and nourished in prayer, especially in the Our Father, the summary of everything that hope leads us to desire.
We can therefore hope in the glory of heaven promised by God to those who love Him and do His will.' (Cf. Rom 8:28-30; Mt 7:21) In every circumstance, each one of us should hope, with the grace of God, to persevere 'to the end' (Mt 10:22; cf. Council of Trent: DS 1541) and to obtain the joy of heaven, as God's eternal reward for the good works accomplished with the grace of Christ. In hope, the Church prays for'all men to be saved.' (1 Tim 2:4) She longs to be united with Christ, her Bridegroom, in the glory of heaven:
Hope, O my soul, hope. You know neither the day nor the hour. Watch carefully, for everything passes quickly, even though your impatience makes doubtful what is certain, and turns a very short time into a long one. Dream that the more you struggle, the more you prove the love that you bear your God, and the more you will rejoice one day with your Beloved, in a happiness and rapture that can never end.' (St. Theresa of Avila, excl.15:3).
When God reveals Himself and calls him, man cannot fully respond to the divine love by his own powers. He must hope that God will give him the capacity to love Him in return and to act in conformity with the commandments of charity. Hope is the confident expectation of divine blessing and the beatific vision of God; it is also the fear of offending God's love and of incurring punishment. (CCC 2090).
Charity--- Charity is the theological virtue by which we love God above all things for His own sake, and our neighbor as ourselves for the love of God.
Jesus makes charity the new commandment (Cf. Jn 13:34). By loving His own 'to the end,' (Jn 13:1) He makes manifest the Father's love which He receives. By loving one another, the disciples imitate the love of Jesus which they themselves receive. Whence Jesus says: 'As the Father has loved Me, so have I loved you; abide in My love.' And again: 'This is My commandment, that you love one another as I have loved you' (Jn 15:9, 12).
Fruit of the Spirit and fullness of the Law, charity keeps the commandments of God and His Christ: 'Abide in My love. If you keep My commandments, you will abide in My love. (Jn 15:9-10; cf. Mt 22:40; Rom 13:8-10).
Christ died out of love for us, while we were still 'enemies' (Rom 5:10). The Lord asks us to love as He does, even our enemies, to make ourselves the neighbor of those farthest away, and to love children and the poor as Christ Himself. (Cf. Mt 5:44; Lk 10:27-37; Mk 9:37; Mt 25:40, 45).
The Apostle Paul has given us an incomparable depiction of charity: 'charity is patient and kind, charity is not jealous or boastful; it is not arrogant or rude. Charity does not insist on its own way; it is not irritable or resentful; it does not rejoice at wrong, but rejoices in the right. Charity bears all things, believes all things, hopes all things, endures all things' (1 Cor 13:4-7).
'If I..... have not charity,' says the Apostle, 'I am nothing.' Whatever my privilege, service, or even virtue, 'if I..... have not charity, I gain nothing' (1 Cor 13:1-4). Charity is superior to all the virtues. It is the first of all the theological virtues: 'So faith, hope, and charity abide, these three. But the greatest of these is charity' (1 Cor 13:13).
The practice of all the virtues is animated and inspired by charity, which 'binds everything together in perfect harmony' (Col 3:14); it is the form of the virtues; it articulates and orders them among themselves; it is the source and the goal of their Christian practice. Charity upholds and purifies our human ability to love, and raises it to the supernatural perfection of divine love.
The practice of the moral life animated by charity gives to the Christian the spiritual freedom of the children of God. He no longer stands before God as a slave, in servile fear, or as a mercenary looking for wages, but as a son responding to the love of Him who 'first loved us' (Cf. 1 Jn 4:19):
If we turn away from evil out of fear of punishment, we are in the position of slaves. If we pursue the enticement of wages,....we resemble mercenaries. Finally if we obey for the sake of the good itself and out of love of Him who commands....we are in the position of children (St. Basil, Reg. tract., prol. 3: PG 31, 896 B.).
The fruits of charity are joy, peace, and mercy; charity demands beneficence and fraternal correction; it is benevolence; it fosters reciprocity and remains disinterested and generous; it is friendship and communion:
Love is itself the fulfillment of all our works. There is the goal; that is why we run; we run toward it, and once wwe reach it, in it we shall find rest (St. Augustine, In ep. Jo. 10, 4: PL 35, 2057).
Apostasy--- the total repudiation of the Christian faith (CCC 2089).
Despair--- By despair man ceases to hope for his personal salvation from God, for help in attaining it or for the forgiveness of his sins. Despair is contrary to God's goodness, to His justice--- for the Lord is faithful to His promises--- and to His mercy. (CCC 2091).
Presumption--- There are two kinds of presumption. Either man presumes upon his own capacities, (hoping to be able to save himself without help from on high), or he presumes upon God's almighty power or His mercy (hoping to obtain his forgiveness without conversion and glory without merit). (CCC 2092).
One can sin against God's love in various ways:
---indifference neglects or refuses to reflect on divine charity; it fails to consider its prevenient (to come before, to anticipate) goodness and denies its power.
---ingratitude fails or refuses to acknowledge divine charity and to return Him love for love.
--- lukewarmness is hesitation or negligence in responding to God's love; it can imply refusal to give oneself over to the prompting of charity.
--- acedia or spiritual sloth goes so far as to refuse the joy that comes from God and to be repelled by divine goodness.
--- hatred of God comes from pride. It is contrary to love of God, whose goodness it denies, and whom it presumes to curse as the one who forbids sins and inflicts punishments.