The Catechism of the Summa - SECOND SECTION - A DETAILED SURVEY OF MAN'S RETURN TO GOD - XXIV. OF THE SINS OF SPEECH COMMITTED IN THE ORDINARY COURSE OF LIFE, VIZ., OF INVECTIVE, OF DETRACTION (AND CALUMNY), OF WHISPERINGS, OF MOCKERY, OF THE CURSE (A)

(A) What are the sins of injustice committed against our neighbour by speech in the ordinary course of life?

They are invective, detraction, whisperings, mockery, and the curse (LXXII.-LXXVI.).
 
What is understood by invective?

Invective is that sin which wounds another, in the honour or in the respect due to him, by words (LXXII. 1).
 
Is it a mortal sin?

Yes, whenever such words attack the honour of another in a grave way. The sin is venial only if our neighbour's honour is not seriously injured, or if one has no intention of seriously injuring another (LXXII. 2).
 
Is one bound in justice to treat others with the reverence due to them?

Yes, one is strictly bound in justice to do this, for the harmony of all living in a society is dependent upon this (LXXII. 1-3).
 
Upon what is this duty founded and what is its importance?

It is founded upon this, that the honour of each one is a thing which men cherish most. Even the least among men has a right to be treated with the respect due to his own particular status in life: to be lacking towards him in respect, whether by word or deed, is to wound him in what he holds most dear (ibid.).
 
One ought then with the greatest care to avoid saying or doing anything whatsoever which may bring disconsolation or humiliation upon our fellow-men?

Yes, one must do this at all cost (ibid.).
 
Is it ever permitted to act otherwise?

This is only permitted in the case of a superior whose duty it may be to correct one under his charge when the latter merits such correction; with this condition, however, that a superior do not do this in the heat of passion, or in a manner that is indiscreet or uncalled for (LXXII. 2, Obj. 2).
 
What should be done with regard to those who are lacking in respect?

With such as these charity, and sometimes justice, demands that their boldness be punished. But in this case it is necessary to be on one's guard lest, in punishing them, one exceed the right bounds imposed by the law and so bring injury to oneself (LXXII. 3).

Next - The Catechism of the Summa - SECOND SECTION - A DETAILED SURVEY OF MAN'S RETURN TO GOD - XXIV. OF THE SINS OF SPEECH COMMITTED IN THE ORDINARY COURSE OF LIFE, VIZ., OF INVECTIVE, OF DETRACTION (AND CALUMNY), OF WHISPERINGS, OF MOCKERY, OF THE CURSE (B)