Whether boasting is a mortal sin?

❌ Objection 1 : It seems that boasting is a mortal sin. For it is written (Prov. 28:25): "He that boasteth, and puffeth himself, stirreth up quarrels." Now it is a mortal sin to stir up quarrels, since God hates those that sow discord, according to Prov. 6:19. Therefore boasting is a mortal sin.

❌ Objection 2 : Further, whatever is forbidden in God's law is a mortal sin. Now a gloss on Ecclus. 6:2, "Extol not thyself in the thoughts of thy soul," says: "This is a prohibition of boasting and pride." Therefore boasting is a mortal sin.

❌ Objection 3 : Further, boasting is a kind of lie. But it is neither an officious nor a jocose lie. This is evident from the end of lying; for according to the Philosopher (Ethic. iv, 7), "the boaster pretends to something greater than he is, sometimes for no further purpose, sometimes for the sake of glory or honor, sometimes for the sake of money." Thus it is evident that it is neither an officious nor a jocose lie, and consequently it must be a mischievous lie. Therefore seemingly it is always a mortal sin.