John Cassian, Conferences I–X V.3: Of the two classes of faults and their fourfold manner of acting on us

Of these faults then there are two classes. For they are either natural to us as gluttony, or arise outside of nature as covetousness. But their manner of acting on us is fourfold. For some cannot be consummated without an act on the part of the flesh, as gluttony and fornication, while some can be completed without any bodily act, as pride and vainglory. Some find the reasons for their being excited outside us, as covetousness and anger; others are aroused by internal feelings, as accidie and dejection.