Chapter VII. On internal sins

394. Notions. Internal sins are called those which are perfected within the heart of man and do not appear outwardly, except perhaps because of an effect accidentally following from them. There are three species of them: morose delectation, joy, desire. - That internal sins, and not only external acts, as the Pharisees thought, are really sins is clear from many texts of Sacred Scripture. Already in the decalogue there is the precept: "Thou shalt not covet."⁷⁴ But in Proverbs it is said: "Evil thoughts are an abomination to the Lord,"⁷⁵ and in the book of Wisdom: "Perverse thoughts separate from God."⁷⁶

The three internal sins enumerated are not only true sins, but are also more dangerous sins, because a) they are more easily perpetrated; b) they are more difficultly avoided; c) they are less cared for. Hence it is better to treat of them specially and individually.

Note. Although internal sins are wont chiefly and more frequently to occur in the matter of lust, nevertheless they can also be in any other evil matter, for example in hatred of neighbor, in injury to justice, etc.

⁷⁴ Deut. 5, 21; cf. Rom. 7, 7 and 13, 9.

⁷⁵ Prov. 15, 26.

⁷⁶ Sap. 1, 3. Cf. Matth. 23, 27.