The mood of The Beautiful and Damned is initially casual and extravagant. It mirrors the thoughts and actions of the characters, especially Anthony and Gloria, as they vie for a place in high society. Here is an example from Chapter 1, in which Anthony travels abroad after college:
Then abroad again—to Rome this time, where he dallied with architecture and painting in turn, took up the violin, and wrote some ghastly Italian sonnets, supposedly the ruminations of a thirteenth-century monk on the joys of the contemplative life. [...] those of them who were abroad that year looked him up and discovered with him, on many moonlight excursions, much in the city that was older than the Renaissance or indeed than the republic. Maury Noble, from Philadelphia, for instance, remained two months, and together they realized the peculiar charm of Latin women and had a delightful sense of being very young and free in a civilization that was very old and free.
This passage conveys the casual extravagance of Anthony's life. The narrator describes Anthony's hobbies and travels in carefree terms: he "dallied with architecture" and "took up the violin." Anthony remains nonchalant about these privileges despite their incredible expense. The parallel between the phrases "young and free" and "old and free" sets up a parallel between Anthony and the city of Rome, underscoring his self-aggrandizing nature. Despite his general incompetence, Anthony believes that he is a great person with every right to inherit his grandfather's fortune. And the mood of casual extravagance reflects this opinion of himself.
At the story's end, however, Anthony finds himself ruined by alcoholism, and the mood turns to one of despair. Throughout the story, his mind and body have deteriorated beyond recognition. And in the final chapter, the narrator compares Anthony and Gloria to "players who had lost their costumes, lacking the pride to continue on the note of tragedy" (175). Interestingly, the mood remains extravagant even though the diction shifts away from casual opulence and toward tragedy and despair. The slight shift in mood suggests that the characters retain an undue sense of self-importance despite being morally and financially bankrupt.
