INGRATITUDE. - It is the disposition of mind (vice) of one who does not acknowledge and does not appreciate benefits received. It may take the concrete form of a purely negative attitude of failing to acknowledge, to thank, or to repay the good received; it may also assume a positive attitude of hostility in one who judges the benefit received to be inferior to his own merit, harmful rather than advantageous, or who repays the benefactor with insults or other injustices.
Morally, ingratitude (the negation of the virtue of gratitude, a specific virtue distinct from piety and religion and a potential part of the virtue of justice) is always a sin. In respect of its object, the sin is considered by common doctrine to be venial, since it does not directly contradict the order of charity; whether by reason of its end (hatred of or contempt for the benefactor) or of its circumstances (e.g., one who, being able, refused to assist a person in need after having received notable benefits from him), it may become a grave fault.
Ingratitude is always a moral fault; in legal systems it is not regarded as an offence; nevertheless, in the cases exhaustively provided for, ingratitude may be grounds for revoking a gift (Cod. civ. it., art. 801). According to the CIC, the ingratitude of the rector of a Church or of its administrators cannot be invoked in order to revoke a donation made to the Church (can. 1536 § 4).