Today’s Catechism sections discuss the first commandment and the Theological Virtues. Supporting material comes from the “Summa Theologica”.

Faith

2087 Our moral life has its source in faith in God who reveals his love to us. St. Paul speaks of the "obedience of faith"9 as our first obligation. He shows that "ignorance of God" is the principle and explanation of all moral deviations.10 Our duty toward God is to believe in him and to bear witness to him.

2088 The first commandment requires us to nourish and protect our faith with prudence and vigilance, and to reject everything that is opposed to it. There are various ways of sinning against faith:
Voluntary doubt about the faith disregards or refuses to hold as true what God has revealed and the Church proposes for belief. Involuntary doubt refers to hesitation in believing, difficulty in overcoming objections connected with the faith, or also anxiety aroused by its obscurity. If deliberately cultivated doubt can lead to spiritual blindness.

2089 Incredulity is the neglect of revealed truth or the willful refusal to assent to it. "Heresy is the obstinate post-baptismal denial of some truth which must be believed with divine and catholic faith, or it is likewise an obstinate doubt concerning the same; apostasy is the total repudiation of the Christian faith; schism is the refusal of submission to the Roman Pontiff or of communion with the members of the Church subject to him."11

Hope

2090 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.

2091 The first commandment is also concerned with sins against hope, namely, despair and presumption:
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.

2092 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).

Charity

2093 Faith in God's love encompasses the call and the obligation to respond with sincere love to divine charity. The first commandment enjoins us to love God above everything and all creatures for him and because of him.12

2094 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 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 divine 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.

In the “Summa Theologica” (Secunda Secundæ Partis, 130, 1), St. Thomas Aquinas discusses the sin of presumption.

Article 1. Whether presumption is a sin?

Objection 1. It seems that presumption is not a sin. For the Apostle says: "Forgetting the things that are behind, I stretch forth [Vulgate: 'and stretching forth'] myself to those that are before." But it seems to savor of presumption that one should tend to what is above oneself. Therefore presumption is not a sin.

Objection 2. Further, the Philosopher says (Ethic. i, 7) "we should not listen to those who would persuade us to relish human things because we are men, or mortal things because we are mortal, but we should relish those that make us immortal": and (Metaph. i) "that man should pursue divine things as far as possible." Now divine and immortal things are seemingly far above man. Since then presumption consists essentially in tending to what is above oneself, it seems that presumption is something praiseworthy, rather than a sin.

Objection 3. Further, the Apostle says (2 Corinthians 3:5): "Not that we are sufficient to think anything of ourselves, as of ourselves." If then presumption, by which one strives at that for which one is not sufficient, be a sin, it seems that man cannot lawfully even think of anything good: which is absurd. Therefore presumption is not a sin.

On the contrary, It is written (Sirach 37:3): "O wicked presumption, whence camest thou?" and a gloss answers: "From a creature's evil will." Now all that comes of the root of an evil will is a sin. Therefore presumption is a sin.

I answer that, Since whatever is according to nature, is ordered by the Divine Reason, which human reason ought to imitate, whatever is done in accordance with human reason in opposition to the order established in general throughout natural things is vicious and sinful. Now it is established throughout all natural things, that every action is commensurate with the power of the agent, nor does any natural agent strive to do what exceeds its ability. Hence it is vicious and sinful, as being contrary to the natural order, that any one should assume to do what is above his power: and this is what is meant by presumption, as its very name shows. Wherefore it is evident that presumption is a sin.

Reply to Objection 1. Nothing hinders that which is above the active power of a natural thing, and yet not above the passive power of that same thing: thus the air is possessed of a passive power by reason of which it can be so changed as to obtain the action and movement of fire, which surpass the active power of air. Thus too it would be sinful and presumptuous for a man while in a state of imperfect virtue to attempt the immediate accomplishment of what belongs to perfect virtue. But it is not presumptuous or sinful for a man to endeavor to advance towards perfect virtue. On this way the Apostle stretched himself forth to the things that were before him, namely continually advancing forward.

Reply to Objection 2. Divine and immortal things surpass man according to the order of nature. Yet man is possessed of a natural power, namely the intellect, whereby he can be united to immortal and Divine things. On this respect the Philosopher says that "man ought to pursue immortal and divine things," not that he should do what it becomes God to do, but that he should be united to Him in intellect and will.

Reply to Objection 3. As the Philosopher says (Ethic. iii, 3), "what we can do by the help of others we can do by ourselves in a sense." Hence since we can think and do good by the help of God, this is not altogether above our ability. Hence it is not presumptuous for a man to attempt the accomplishment of a virtuous deed: but it would be presumptuous if one were to make the attempt without confidence in God's assistance.

Footnotes

9 ⇒ Rom 1:5; ⇒ 16:26.
10 Cf. ⇒ Rom 1:18-32.
11 ⇒ CIC, can. 751: emphasis added.
12 Cf. ⇒ Deut 6:4-5.