p. 64:

Everyone suspects himself of at least one of the cardinal virtues, and this is mine:  I am one of the few honest people that I have ever known.

There are so many reasons why Nick’s ‘suspicion’ here is probably false, even though it is an assertion about himself.  He’s an unreliable narrator:  self-admittedly distracted, occasionally drunk, absorbed in his own career and love life and ego.  His statement is boastful no matter how mild the language, and immodest claims of high character are usually false.

But of all the reasons to doubt Nick’s self-assessment, I’ll highlight this one:  He’s only a few days shy of his 30th birthday.  That’s too small a percentage of an expected lifespan to judge one’s own possession of a cardinal virtue.  Think about the changes that people make in the years after 30:  wild partiers become sedate homemakers, stable careerists become out-of-control addicts, atheists find a higher power while the devout renounce their gods.

We can’t know yet whether Nick deserves to stand with the few honest people in the world. We don’t have any reason to believe that he’s ever been tested, and we have every reason to believe that the final judgment of his character will take many more years to make.

Finally (and pedantically), honesty isn’t even one of the cardinal virtues . . . which I suppose should have been the first thing to tip us off to Nick’s (self-)deception.