Seeing others through a spyglass

Proust spends time pondering the nature of people's shortcomings, for he says, "Each of our friends has his defects..." and adds, "...the variety of our defects is no less remarkable than the similarity of our virtues."

Proust reflects on self-awareness and appearances.

"Since the risk of giving offense arises principally from the difficulty of appreciating what does and what does not go unnoticed, we ought to at least, from prudence, never to speak of ourselves, because that is a subject on which we may be sure that other people's views are never in accordance with our own."

"Moreover it seems that our attention, always attracted by what is characteristic of ourselves, notices [defects] more than anything else in other people. One short-sighted man says of another: 'But he can scarcely open his eyes!'; a consumptive has his doubts as to the pulmonary integrity of the most robust; an unwashed man speaks only of the baths that other people do not take; an evil-smelling man insists that other people smell; a cuckold sees cuckolds everywhere. Then, too, every vice, like every profession, requires and develops a special knowledge which we are never loathe to display. And it is not only when we speak of ourselves that we imagine other people to be blind; we behave as though they were."
(emphasis mine)

Any page now, we will meet the Baron De Charlus, of the Guermantes family, and the meaning will become clear.

There is a passage I didn't quote where Proust says of homosexuality, "The inverts sniff out inverts." Proust was the first modern novelist to write openly about gays and lesbians.