Final answer:
The theme suggested by the narrator's realization in Paris is the importance of holding on to the past, as seen through literary references that highlight the lingering influence of bygone eras on the present.
Step-by-step explanation:
The narrator's realization in Paris suggests a theme of the importance of holding on to the past. This is evident from various literary references that emphasize the impact of the past on the present. Glasgow's depictions of hauntings by the past, as well as the writings of others like Fitzgerald, reflect the lasting influence of bygone days and lost opportunities. Descriptions of characters who are anchored by their memories, such as the old man reminiscing about the Confederacy, or artists like Chagall reflecting on their homeland while in Paris, all convey the powerful connection to the past. Moreover, the concept of nostalgia, or the yearning for a return to a romanticized past, is often juxtaposed against the harsh light of present reality.