Northanger Abbey explores the joys (and sorrows) of friendship. The first major friendship in the novel is between two families: the Allens and the Morlands. This connection leads to the Allens inviting Catherine on a trip to Bath. The story also explores friendship between individuals like Catherine and Isabella. In Volume 1, Chapter 4, they meet in the Pump-room (one of the central meeting points in Bath):
[Catherine] was soon invited to accept an arm of the eldest Miss Thorpe, and take a turn with her about the room. Catherine was delighted with this extension of her Bath acquaintance, and almost forgot Mr. Tilney while she talked to Miss Thorpe. Friendship is certainly the finest balm for the pangs of disappointed love[...]. Miss Thorpe, however, being four years older than Miss Morland, and at least four years better informed, had a very decided advantage in discussing such points; she could compare the balls of Bath with those of Tunbridge[...].
Here, Catherine and Isabella Thorpe "take a turn" about the drawing-room. Isabella is much more experienced and cultured, but she manages to make Catherine feel comfortable. Friendship is metaphorically presented as the "finest balm" for Catherine's disappointment at Henry's absence. This metaphor shows that friendship can evolve in a context of sorrow and helps distract one from heartbreak or unrequited love much like medicine or "balm" can be invented to cure pain or illness.
However, later in the story, the reader discovers that Isabella is merely a conniving social climber who makes nice to Catherine in hopes of marrying her brother James. So friendship indeed turns out to be a "balm," but rather than one offered to Catherine out of the kindness of Isabella's heart, it is one developed to prevent Isabella's romantic disappointment and help her achieve the marriage of her dreams.
Austen was known for her skillful social dramas, and Northanger Abbey exemplifies her ability to portray relationships. The recurring motif of friendship places continuous emphasis on interpersonal relations.
Austen's social satires often emphasize the follies of marriage. In Northanger Abbey, she expresses her view of marriage through the character of Henry Tilney, who (in Volume 1, Chapter 10) uses dancing as a metaphor for matrimony:
And such is your definition of matrimony and dancing. [...] You will allow, that in both, man has the advantage of choice, woman only the power of refusal; that in both, it is an engagement between man and woman, formed for the advantage of each; and that when once entered into, they belong exclusively to each other till the moment of its dissolution; that it is their duty[...] and their best interest to keep their own imaginations from wandering towards the perfections of their neighbours, or fancying that they should have been better off with anyone else.
The clarity with which Henry explains this metaphor demonstrates his erudition and rhetorical skill, but it also carries a hint of cynicism. He says that marriage is to the "advantage of each" when entered into while acknowledging that women have only the power of refusal (not choice) in the first stages. This is an excellent extended metaphor because Henry is able to explain how each element of one is like the other. He goes on to admit that the two activities are dissimilar in some ways, but he still believes in the strength of his metaphor. Catherine, who can believe almost anything, ironically cannot accept Henry's analogy.
