Summa summae S. Thomae, Tomus III

[The sins opposed to hope are of two kinds: some of them are contrary to the desire for eternal beatitude, others to the confidence of obtaining it.

I say 1°: To the desire for eternal beatitude are opposed: 1° the affection of this age, whereby earthly things are desired more than eternal ones; 2° a disordered affection for heavenly felicity, whereby out of weariness of life and labor ultimate happiness is sought.

The former affection is a mortal sin if earthly things are set up as the ultimate end: e.g., if one were so disposed as to wish to dwell perpetually in the present life and to leave heaven to God, if God were willing to leave him the earth. The latter does not exceed venial, unless there be present an express rebellion against divine providence. One may licitly wish for his own death in order to avoid sin or some other immense evil, provided he submit himself to the divine will,¹ and in no other sense than the Apostle when he says, Rom., VII, 24: Unhappy man that I am! who will deliver me from the body of this death?

I say 2°: To the fiducial expectation of eternal beatitude there is opposed, by way of defect, despair; by way of excess, presumption.

1° Despair is « a giving over of the soul, or a movement of the will, whereby one refuses to attain beatitude through the ordinary means. » It is also defined otherwise, « a want of confidence in obtaining beatitude, or the means necessary for obtaining it. »

Despair is a sin; which the Angelic Doctor proves thus, here q. 20, a. 1, o: « Every appetitive movement conformed to true understanding is good in itself; but every appetitive movement conformed to false understanding is evil in itself and sin. Now the true judgment of the intellect concerning God is that salvation comes from Him, and pardon is granted to sinners...; but it is a false opinion that forgiveness is denied to a repentant sinner, or that God does not convert sinners to Himself through justifying grace. And therefore, just as the movement of hope, which conforms to true judgment, is praiseworthy and virtuous; so the opposite movement of despair, which conforms to a false judgment about God, is vicious and a sin. »

This sin is mortal, and indeed most grievous, yet less than the sin of unbelief and hatred of God, but more dangerous, as is shown by the same Doctor, ibid., a. 3, o: « That which has aversion from God first and in itself is the most grievous sin among mortal sins. Now to the theological virtues are opposed unbelief, despair, and hatred of God: among which hatred and unbelief, if compared with despair, are found in themselves, that is according to the account of their own species, graver. For unbelief arises from this, that man does not believe the very truth of God; hatred of God from this, that man's will is opposed to the divine goodness itself; but despair from this, that man does not hope to partake of the goodness of God. From this it is evident that unbelief and hatred of God are against God as He is in Himself, but despair as His good is partaken of by us. Hence it is a greater sin, speaking absolutely, not to believe the truth of God, or to hate God, than not to hope to obtain glory from Him. But if despair be compared to those two sins on our part, then despair is more dangerous; because by hope we are recalled from evils and led on to pursue goods. And therefore, when hope is taken away, men unrestrained fall into vices and are withdrawn from laborious goods... And Isidore says in his book de Summo bono: « To commit any crime is the death of the soul; but to despair is to descend into hell. »

It follows that despair properly so called admits no parvity of matter, although at times it may become venial, owing to a defect of full consent.² Therefore the confessor must examine whether, out of an affect of despair, the customary exercises of piety have been intermitted, especially while the precept urged, or not. Thence he will have a sufficiently safe indication of consent given or refused. He should note, however, that many penitents despair not of God's mercy, but of their own cooperation with His grace; which ought not properly to be called despair, but is pusillanimity, which admits parvity of matter.

2° Presumption, which is more frequent than despair, arises from a defect of the fear of God, and is defined: « A rash expectation of beatitude or of the means thereto. »

It is a sin, and indeed, according to St. Thomas, here q. 21, a. 1, o, « it is properly a species of sin against the Holy Ghost, because by such presumption the aid of the Holy Spirit, whereby man is recalled from sin, is removed or contemned. »

It is a grave sin in itself, which is not excused from being so, save by the imperfection of the act. The Angelic Doctor gives the reason, ibid., a. 2, o: « As was said above concerning despair, every appetitive movement which conforms to false understanding is evil in itself and sin. But presumption is a certain appetitive movement, because it imports a certain disordered hope; and it conforms to false understanding, as does despair. For if it is false that God does not grant forgiveness to penitents, or that He does not convert sinners to penance; so too it is false that He grants forgiveness to those persevering in sin, and bestows glory on those ceasing from good work: to which judgment the movement of presumption conforms itself. And therefore presumption is a sin, yet less than despair; because it is more proper to God to have mercy and to spare than to punish, on account of His infinite goodness. For the former belongs to God in Himself, the latter on account of our sins. »

Hence: 1° He sins who hopes for salvation either on account of his own merits, or on account of the merits of Christ, without any cooperation of his own works.³ — 2° Likewise he sins mortally who, in hope of pardon, is induced to sin, because, e.g., God forgives many sins as easily as one. But it is otherwise if he were to say that he would confess many sins as easily as one: which of itself is only venial.⁴ — 3° He contracts no guilt of presumption properly so called who sins in hope of pardon, so that this hope is not the motive of sinning, but merely accompanies the sin. — 4° Those who persevere in sin in the hope of repenting sometime are with difficulty excused from grave sin against the charity due to themselves, since they expose themselves to great danger of damnation.⁵

It must be observed that with the sin of either despair or presumption there is sometimes joined the sin of heresy, e.g., if one were to judge, like Cain, his own sin to be unforgivable; or if one were to hope for salvation by the sole powers of nature, as the Pelagians; or by faith alone, without works, as the Lutherans.]