How to explain the inexplicable things that men do, such as make up stories about themselves? Simply because of the vanity through which they are affected:
We are vain of the surprizing adventures which we have met with, the escapes which we have made, the dangers to which we have been exposed; as well as of our surprising feats of vigour and activity. Hence the origin of vulgar lying; where men, without any interest, and merely out of vanity, heap up a number of extraordinary events, which are either the fictions of their brain; or, if true, have no connexion with themselves. Their fruitful invention supplies them with a variety of adventures; and where that talent is wanting, they appropriate such as belong to others, in order to gratify their vanity: For betwixt that passion, and the sentiment of pleasure, there is always a close connexion.
Why make up stories? Human beings are profoundly irrational, Hume has shown it.
By wanting to make themselves interesting, some men attempt to tie to themselves, through a relation of property, events that would confer them greater importance, because prone to more attention from other people (and in particular those they find desirable).
But property, as it gives us the fullest power and authority over any object, is the relation, which has the greatest influence on these passions.
What brings us pleasure suddenly appears much more reasonable.
It is therefore merely in order to “flatter their pride”—feeling of pleasure by excellence according to Hume—that men behave in such vain, misleading ways—and surely against reason.
It is very often the case in love—since the object of pride (thus pleasure) is, precisely, the Self.