Objection 1. It would seem that contention is not a daughter of vainglory. For contention is akin to zeal, wherefore it is written (1 Corinthians 3:3): "Whereas there is among you zeal [Douay: 'envying'] and contention, are you not carnal, and walk according to men?" Now zeal pertains to envy. Therefore contention arises rather from envy.
Objection 2. Further, contention is accompanied by raising of the voice. But the voice is raised on account of anger, as Gregory declares (Moral. xxxi, 14). Therefore contention too arises from anger.
Objection 3. Further, among other things knowledge seems to be the matter of pride and vainglory, according to 1 Corinthians 8:1: "Knowledge puffeth up." Now contention is often due to lack of knowledge, and by knowledge we do not impugn the truth, we know it. Therefore contention is not a daughter of vainglory.
On the contrary stands the authority of Gregory (Moral. xxxi, 14).
I answer that, As stated above (Question 37, Article 2), discord is a daughter of vainglory, because each of the disaccording parties clings to his own opinion, rather than acquiesce with the other. Now it is proper to pride and vainglory to seek one's own glory. And just as people are discordant when they hold to their own opinion in their hearts, so are they contentious when each defends his own opinion by words. Consequently contention is reckoned a daughter of vainglory for the same reason as discord.
Reply to Objection 1. Contention, like discord, is akin to envy in so far as a man severs himself from the one with whom he is discordant, or with whom he contends, but in so far as a contentious man holds to something, it is akin to pride and vainglory, because, to wit, he clings to his own opinion, as stated above (37, 2, ad 1).
Reply to Objection 2. The contention of which we are speaking puts on a loud voice, for the purpose of impugning the truth, so that it is not the chief part of contention. Hence it does not follow that contention arises from the same source as the raising of the voice.
Reply to Objection 3. Pride and vainglory are occasioned chiefly by goods even those that are contrary to them, for instance, when a man is proud of his humility: for when a thing arises in this way, it does so not directly but accidentally, in which way nothing hinders one contrary from arising out of another. Hence there is no reason why the "per se" and direct effects of pride or vainglory, should not result from the contraries of those things which are the occasion of pride.
Source: Summa Theologica (New Advent)