BITE-SIZE THEOLOGY (196): What are internal sins and sins against the Holy Spirit?

Rev José Mario O Mandía 


Sin can be committed not only through external acts or omissions, but also through our thoughts and desires. These are called “internal sins.” Psalm 19:12-13 asks the Lord, “Clear me from hidden faults. Keep back thy servant also from presumptuous sins; let them not have dominion over me! Then I shall be blameless, and innocent of great transgression.”

We need to be wary of internal sins because (1) they are more easily committed; (2) they are more difficult to avoid; and (3) we pay less attention to them.

Our Lord warned about internal sins, as for instance when He taught: “You have heard that it was said, ‘You shall not commit adultery.’ But I say to you that every one who looks at a woman lustfully has already committed adultery with her in his heart” (Matthew 5:27-28).

“For out of the heart come evil thoughts, murder, adultery, fornication, theft, false witness, slander” (Matthew 15:19).

“Woe to you, scribes and Pharisees, hypocrites! for you are like whitewashed tombs, which outwardly appear beautiful, but within they are full of dead men’s bones and all uncleanness. So you also outwardly appear righteous to men, but within you are full of hypocrisy and iniquity” (Matthew 23:27-28).

Internal sins are sins committed in the heart of man. Moralists usually classify them into three types:

(1) Deliberate pleasure (Delectatio morosa). It is sinful complacency in an evil act presented to the imagination with no desire to perform the act. How serious is it? If the evil act presented to the imagination is grave, then the deliberate pleasure is grave.

(2) Sinful joy (Gaudium peccaminosum). It is taking pleasure in an evil act done in the past. If the evil act was grave, then the sinful joy is grave.

(3) Evil desire (Desiderium pravum). It is deliberate pleasure in some sin not yet committed, but with a desire to commit it.


Jesus spoke about the sin that cannot be forgiven. The CCC (1864) teaches: “‘Therefore I tell you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven’ (Matthew 12:31; cf. Mark 3:29; Luke 12:10). There are no limits to the mercy of God, but anyone who deliberately refuses to accept his mercy by repenting, rejects the forgiveness of his sins and the salvation offered by the Holy Spirit (cf. John Paul II, Dominum et Vivificantem, 46). Such hardness of heart can lead to final impenitence and eternal loss.”

When a person refuses the grace of contrition and forgiveness, he is rejecting the action of the Holy Spirit. This is why such sin cannot be forgiven because the person himself does not want to be forgiven. We sin against the Holy Spirit when we refuse to confess our sins in the Sacrament of Penance: “Confession is of no use.”

To sin against the Holy Spirit is to voluntarily close one’s heart and make it impermeable to the action of grace. This reminds us of the Psalm that talks about Israel’s experience in the wilderness. “O that today you would hearken to his voice! Harden not your hearts, as at Meribah, as on the day at Massah in the wilderness, when your fathers tested me, and put me to the proof, though they had seen my work. For forty years I loathed that generation and said, ‘They are a people who err in heart, and they do not regard my ways.’ Therefore I swore in my anger that they should not enter my rest” (Psalm 95:7-11).