Themes in Lolita - self-delusion
The first time Humbert Humbert lists historical figures who took chid brides it is defensively. The second time it is with almost whistul envy. He speaks of cultures where it is acceptable for a grown man to marry a sixteen year old but not a twelve year old, as if it's just a matter of a small measure when he himself (as we see from his Parisian prostitute) is the most aware of the difference.
He lists how doctors have categorised child, to girl-child, to young person, and the laws surrounding it. He discusses signs of pubescence. This clinical delineation isn't just about his attraction (he uses far more poetic language for that), it is to delineate what he sees as boundaries between full-on child molestation and his lesser paedophilia: these lines categorise his 'nymphets' as being something other than pure children. He says the term 'nymphet' refers to those girls somehow posessed and without childhood innocence to besmirch, the implication being this makes his crime less. Of course his nymphet category is spurious, because these are just the girls he fancies.
There has been a lot of self-delusion so far, but also a lot of self-knowledge and reflection. He's a very interesting and by turns disgusting and pitiable character.