Two themes that Austen addresses in Persuasion, which had both cultural and personal significance for Austen, are those of constancy in love and long engagements. One reason Lady Russell was opposed to Anne's engagement to Frederick Wentworth when they first met when Anne was nineteen was that his youth and low rank in the navy rendered the necessity of a long engagement between them: they would not be allowed to marry until after Wentworth had advanced in rank and acquired a reasonable fortune from the booty of war. Lady Russell could not countenance Anne tying herself in such a dependent situation at such a young age with so little hope of Wentworth's ambitions being fulfilled in such an "uncertain" profession as being a seaman in times of war.
[Wentworth] had nothing but himself to recommend him, and no hopes of attaining affluence, but in the chances of a most uncertain profession, and no connexions to secure even his farther rise in the profession, would be, indeed, a throwing away ... [of] Anne Elliot, so young; known to so few, to be snatched off by a stranger without alliance or fortune; or rather sunk by him into a state of most wearing, anxious, youth-killing dependence! It must not be,....
The theme of long engagement is taken up again later with energy by the Mmes. Croft and Musgrove while Anne is visiting with them in Bath. The ladies agreed that it was better to let a young couple marry with modest resources and to let them struggle through together than to prevent them from marrying thereby forcing them into a long and uncertain engagement. Both ladies were clear in their adamant support for marriage being delayed no longer than six or twelve months at the outside.
It was felt that the strain of a long engagement was an unnecessary and false dependency and the source of loss of psychological health for the couple.
The theme of constancy in love was introduced in the same scene when Captain Harville beckons to Anne to join him for a word in the window alcove where he is standing. Captain Harville shows Anne a miniature ivory painting of Captain Benwick that had been painted earlier in Cape Town, South Africa. Benwick had had it painted for his then betrothed, Harville's sister Fanny. Harville explained with great emotion that he had been asked by Benwick to have it put in a new setting so that it might be given to Louisa, whose love had replaced that of the dead and deeply mourned Fanny.
Spurred by Benwick's change of affections from Fanny to Louisa, Harville and Anne engage in a deeply felt conversation about whether it is men or women who have a capacity for enduring love, for constancy in love for someone who is either taken in death or taken through some other circumstances, such as Anne's circumstances of a counselor's persuasion against marriage.
"And with a quivering lip [Captain Harville] wound up the whole by adding, "Poor Fanny! she would not have forgotten him so soon!"
"No," replied Anne, in a low, feeling voice. "That I can easily believe."
"It was not in her nature. She doted on him."
"It would not be the nature of any woman who truly loved."
Captain Harville smiled, as much as to say, "Do you claim that for your sex?"
It is this conversation about constancy in love, overheard by Captain Wentworth, that gives Anne and Wentworth a renewed chance at finding and fulfilling their love for each other because, afterward, Wentworth writes Anne his compelling message: "I can listen no longer in silence. I must speak to you by such means as are within my reach. You pierce my soul. I am half agony, half hope. Tell me not that I am too late,...."
These themes had compelling cultural significance, as the examples of Anne, Wentworth, Henrietta and Louisa illustrate. We can speculate about the significance these themes had for Jane Austen personally because of two events in her own life. Jane met, during a summer outing at Lyme, a young navy officer who, like Wentworth, was just starting his navy career; he had prospects but no independent wealth that would allow him to marry. It is believed that they became secretly promised to each other in what they expected would be a long engagement. To Jane's sorrow, the young man never returned, having been killed at sea. Jane's letters also reveal that while visiting her brother, she accepted the proposals of a old family friend, but then fled immediately the next morning leaving a message of her regrets. It is sometimes speculated that at least part of the reason Jane fled from that marriage is that the constancy of her love lent her heart, like Anne's heart, room only for her love for her lost sailor.