For lying is opposed to truth. But it is possible to boast even without lying, as when a man makes a show of his own excellence.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic truth boasting
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/18755/pg18755-images.html

Context

“Whether it is a mortal sin? _______________________ FIRST ARTICLE [II-II, Q. 112, Art. 1] Whether Boasting Is Opposed to the Virtue of Truth? Objection 1: It seems that boasting is not opposed to the virtue of truth. For lying is opposed to truth. But it is possible to boast even without lying, as when a man makes a show of his own excellence. Thus it is written (Esther 1:3, 4) that Assuerus "made a great feast . . . that he might show the riches of the glory" and "of his kingdom, and the greatness and boasting of his power." Therefore boasting is not opposed to the virtue of truth.” source