Throughout the story, Mrs. Sommers seems to operate on some inexplicable impulse. The source of this impulse (repressed desire) soon becomes clear as she reverts back to her former habits of big spending and seeking comfort in luxurious places. Describing her motivation as an impulse also divests her of responsibility. This concept first appears when she puts on the stockings and leans back in a comfortable chair:
She was not thinking at all. She seemed for the time to be taking a rest from that laborious and fatiguing function and to have abandoned herself to some mechanical impulse that directed her actions and freed her of responsibility.
Here, a "mechanical impulse" replaces conscious, intentional action. Importantly, this motivational shift frees Mrs. Sommers of responsibility. As the story progresses, the impulse toward comfort seems to grow stronger. The restaurant scene parallels the stocking scene in its emphasis on Mrs. Sommers's undeniable impulse:
Another time she would have stilled the cravings for food until reaching her own home, where she would have brewed herself a cup of tea and taken a snack of anything that was available. But the impulse that was guiding her would not suffer her to entertain any such thought.
At the restaurant, Mrs. Sommers feels the strong pull of delicious delicacies. Instead of waiting to dine frugally at home, she acts on her desire for fine dining. She heeds, in other words, an impulse toward lavishness. In doing so, she defies her expected duties as a responsible, frugal family woman living in the late 19th century. But the story suggests, by the end, that she is unable to truly escape her responsibilities. Her impulse toward satisfaction and pleasure doesn't necessarily give her what she really wants, which—as the end of the story makes clear—is a genuine sense of freedom from her restrictive life.
Luxury is a prominent motif in "A Pair of Silk Stockings." The first iteration appears when Mrs. Sommers discovers the stockings. Their silky, slinky texture contrasts sharply with her common cotton stockings:
How good was the touch of the raw silk to her flesh! She felt like lying back in the cushioned chair and reveling for a while in the luxury of it. She did for a little while. Then she replaced her shoes, rolled the cotton stockings together and thrust them into her bag.
Here, the relationship between feeling and doing reveals the profound temptation of luxury. Once Mrs. Sommers feels the stockings, she is compelled to indulge in a string of luxurious activities. Just after she buys them, she immediately goes to purchase a pair of boots. Then she realizes she's hungry, and instead of waiting to get home to eat leftovers, she chooses a fancy luncheon at a fashionable restaurant. Finally, temptation appears in the form of a theater poster:
There was still money in her purse, and her next temptation presented itself in the shape of a matinée poster. It was a little later when she entered the theatre, the play had begun and the house seemed to her to be packed. But there were vacant seats here and there, and into one of them she was ushered, between brilliantly dressed women who had gone there to kill time and eat candy and display their gaudy attire.
The theater scene offers a powerful conclusion to Mrs. Sommers's day of luxury. The crowd is full of fashionable people whose "gaudy" clothing rivals the show onstage. But the truly interesting element of luxury here is that of emotion, as Mrs. Sommers "laughed at the comedy and wept [...] over the tragedy." Here, emotion becomes a commodity for purchase. Theater becomes the ultimate form of escapism; the act of buying a ticket is a conscious effort to spend time in another world. Mrs. Sommers is not merely one of the rich people who want to "kill time" by watching performances. She also wants, as she does when buying clothes and food, to escape from her life and responsibilities. All of these activities ensconce Mrs. Sommers in a dreamlike—yet temporary—haze of comfort and luxury.