Act 3

Lady Bracknell and her ideas of marriage are extremely interesting topics. She is basically a parody on the importance of society. She speaks as if society is the only thing that matters.  She  feels that marriages are the way that you need to move up in society, so she is tying to make matches within the play that make sense for advancements in society. She talks of celcily's chin being suitable for society , and then decides that something that unchangable about a person is a thing that can decide whether or not they are worthy of society.
This is likely a comment on how shallow the makings of marriages are In high society.  They become about money and land and appearance, as lady Bracknell points out in her various assessments of the men and women in the play. Marriage, to her, is not at all about love or attraction, but about where it puts you in society.