The main theme in this novel is the danger of excessive sensibility. Austen is concerned with the prevalence of the "sensitive" attitude in the romantic novel which, after the 1760s, turned to emphasizing the emotional and sentimental nature of people rather than, as before, their rational endowments. The influences which worked this change were many. The philosophy of Lord Shaftesbury was popular at the time, stressing man's natural beneficence. Rousseau wrote about the "noble savage," and Samuel Richardson's intense portrayals of the emotional life of women were also popular. The gothic revival was developing at the time, with its stress on the exotic and its accompanying disgust with the trivialities of everyday life. And there was a prevalence of female novelists, writing for a large female audience. The book that brought this genre into the fore was a work by Henry MacKenzie called The Man of Feeling. Tears and sighs were streaming from every chapter. To be able to show one's emotions was thus desirable, and restraint, in fact everything relating to rational control, was deemed artificial. Austen tries to discredit this trend towards sentimentality by pointing out its dangers in the example of Marianne and showing the superiority of sense, in the example of Elinor.
There is a dual plot and dual heroines. Elinor and Marianne each pursues her romance according to her temperament and beliefs. Each has an unhappy love affair at the start. The parallel plots, illustrating the dual theme, are one of the weaknesses of the novel, for they occur too "conveniently" and are therefore not convincing.
The theme of sensibility is illustrated in the love affair between Marianne and Willoughby. The theme of sense begins with the relationship of Elinor and Edward. The two plots are carefully interwoven. Marianne's romance is ideal until Willoughby deserts her. Elinor's is threatened from the start. Marianne's reactions are always impassioned and uncontrolled; Elinor is always sensible and restrained.
Sense is finally justified and sensibility shown to be a weakness. Ironically, Marianne marries a prosaic older man, and for both it is a second love, something Marianne vowed she could never tolerate. Elinor's fate is more romantic; she marries her first and only love and is quite happy to settle down as the wife of a country parson.
Austen, in expostulating this theme, is setting up in the process what she believes to be a fitting standard of behavior. But the issues are not so clear cut. The proponents of sensibility actually emerge as much more favorable characters than do those that stress the tenets of sense. The moral qualities of goodness and loyalty to one's family are an integral part of what Austen means by good sense. In fact, they are the most important parts of it. Thus Marianne and her mother, while immature and overly romantic, are, on the whole, good people. Sir John is much more pleasing than his wife, and Mrs. Palmer is preferable to Mr. Palmer for just those qualities of feeling that he abhors. Willoughby, John and Fanny Dashwood, and Mrs. Ferrars, the villains of this novel, all lack the necessary human sentiments. Only Elinor and Colonel Brandon remain unscathed, and both have ample portions of both sense and sensibility.
Austen is mirroring the basic tension of her times in this work. Reason, the eighteenth-century symbol of all that is good, and the accompanying moral order of the times, which is exemplified in the standards of the community at large, are being challenged by the nineteenth-century romantic strain, where morality is interpreted by the individual. What was to result is literary history.