One of the predominant themes Faulkner explores throughout his classic short story "A Rose for Emily" concerns tradition versus progress. Faulkner examines the theme by illustrating the various ways people treat and view Miss Emily as time passes. Miss Emily Grierson and her outdated home represent the traditional Antebellum South. Her character is even referred to as a "tradition, a duty, and a care"; she is compared to a "fallen monument," and she is respected by older members of Jefferson's community. Individuals of Colonel Sartoris's generation honored Miss Emily by remitting her taxes following the death of her father. However, the newer generation of aldermen sends a deputation to her home insisting that she pay her taxes. However, they are rebuffed by Miss Emily, who instructs them to consult the deceased General Sartoris. Miss Emily's refusal to acknowledge Sartoris's death illustrates her inability to adapt to the changing culture and recognize the transience of time.

Homer Barron’s character also represents the conflict between tradition and progress in Jefferson’s community when he arrives from the North to pave the town’s sidewalks. Homer Barron’s character represents Northern business interests following the Civil War, and he proceeds to court Miss Emily, which upsets the traditionalists in the community. Tragically, Miss Emily fears that Homer will leave her and proceeds to murder him. Unlike the rapidly changing Jefferson community, which is modernizing and moving away from traditional values, Miss Emily remains in a timeless vacuum, inside her decaying home, after she murders Homer Barron. She becomes a reclusive, enigmatic figure, who does not leave her home. Following Miss Emily's funeral, the townspeople break down her attic door to discover Homer Barron's skeleton in a dust-filled bridal suite. The macabre bridal chamber illustrates Miss Emily's inability to adapt to the changing culture or acknowledge the passage of time. The plight of Miss Emily’s life parallels that of the Antebellum South, which has become a haunted distant memory.

The previous posts do a nice job of discussing some of the themes present in "A Rose for Emily."  One theme that hasn't been discussed is the theme of isolation.  

Miss Emily is a lonely and isolated character.  The opening sentence of the story directly tells readers that bit of information.  

When Miss Emily Grierson died, our whole town went to her funeral: the men through a sort of respectful affection for a fallen monument, the women mostly out of curiosity to see the inside of her house, which no one save an old man-servant -- a combined gardener and cook -- had seen in at least ten years.

Emily isolated herself from the town.  Sometimes it's the town and the people of the town that cause a particular person to become isolated; however, Faulkner drops a lot of evidence that suggests that Miss Emily is the main person in control of her isolation.  

After her father's death she went out very little; after her sweetheart went away, people hardly saw her at all.

The above quote shows that Emily didn't make efforts to leave her house.  She chose to isolate herself from the community.  To the credit of the community, the people made efforts to engage with Emily.  Emily simply didn't reciprocate.  

So she vanquished them, horse and foot, just as she had vanquished their fathers thirty years before about the smell.... A few of the ladies had the temerity to call, but were not received, and the only sign of life about the place was the Negro man -- a young man then -- going in and out with a market basket.

I can understand Emily wanting to isolate herself while mourning for her father, but her isolation continues for years.  Her isolation breaks for a bit, and it's important enough for the narrator to make note of it.  

From that time on her front door remained closed, save for a period of six or seven years, when she was about forty, during which she gave lessons in china-painting.

Other than that, Emily's isolation from the town is complete.

One of the themes of "A Rose for Emily" is the constant struggle between the past and the present. Emily cannot let go of the past, especially the attitudes and customs of her father's generation. She believes in the importance of heredity and aristocracy and is holding on to the antebellum beliefs of the past. Colonel Sartoris's decree that Emily is exempt from paying taxes in Jefferson give Emily a license to live as if she is above everyone. Sleeping with Homer's dead body symbolizes Emily's inability to let go of the past and embrace the new ideas of the next generation.

Faulkner gradually reveals this theme through the attitudes of the characters. Emily treats her servant Tobe almost as if he is a slave. The townspeople are just as bad as Emily because they allow her to behave the way she does. When Emily asks for rat poison the clerk allows her to buy it even though she never states its purpose when she is asked.  Although the town officials ask Emily to pay taxes, they never try hard enough to succeed. The subtle passivity and backwardness of the town allow Emily to grow stranger as the story progresses, building to the shocking climax of discovering that Emily had been sleeping next to Homer's dead body for years.

There are many themes within "A Rose for Emily," most of them are pretty common Faulkner themes; the decline of the old south, death, and isolation, among others. The themes are communicated through the plot of the story. Death, for example, occurs five times in "A rose for Emily." Section one even begins with a description of Emily's funeral.