Technological Progress
Though technology in the early 1800s was not nearly what it is today - telephone, motion picture, vaccines, and even the typewriter were all invented in the late 1800s - scientists and inventors were already contemplating mechanical imitation of human movement and behavior. In fact, the first humanoid robot, or automaton, was a soldier with a trumpet, made in 1810 by Friedrich Kauffman in Dresden, Germany. Hoffmann was likely influenced by this recent advance in technology just hours away from his home in Berlin, and the contemplation of the signs of life one should look for and appreciate in others was clearly of interest to him in the writing of The Sandman.
Religion
Religion plays an interesting role in The Sandman, as Coppelius is depicted by Nathanael and the narrator as a devilish, demonic, horrifying man (complete with imagery of pain and fire), but also likened to God in that he is attempting to create life. Specifically, Coppelius himself references God when he attacks Nathanael as a child, saying, "They don't fit properly! It was all right as it was! The Old Man knew what he was doing!" This moment can be read as instilling the story with a moral that one should not attempt to imitate life because the result will be failure and perhaps horror.
Women
Women, their treatment, and their place in society is very important to the story and is demonstrated predominantly through Nathanael's interactions with Clara and Olimpia. Nathanael, and other men in society, obviously seek out women who will be quietly attentive to them - Nathanael remarks specifically on Olimpia's talent of not having to knit, play with a small animal, or even yawn while being read to at length. Hoffmann makes clear that he is parodying this view of women by remarking that after Olimpia is found to be an automaton, men are forced to seek out signs of life in their wives by allowing them to express themselves during reading and discussions. Furthermore, Nathanael's infatuation with the "perfect woman" turns him insane, while Clara's more moderate depiction of womanhood allows her a pleasant life with a husband and two children, which the reader is left with at the end of the story.
Beauty
Clara and Olimpia are both described as beautiful in terms of their proportions and features, but something is missing in each that makes them not fully "beautiful." This idea of beauty and perfect womanhood is important, because it is clear that men want women to be both strict with themselves (not speaking, not yawning, thin, graceful) but need some sign of liveliness (perhaps an attractive youthfulness) to make them seem less mechanical and thus live up to true beauty. The narrator's section on artists' view of Clara is especially important because it differentiates artistic beauty, or at least things that artists find beautiful, from beauty to the general population, indicating that artists focus more on the beauty of parts than the beauty and liveliness of the whole.
Writing and Writers
There are three important levels of writers to this story: Nathanael, the story's narrator and supposed author, and Hoffmann himself. What is demonstrated through all of them is two things - that they write and publish work not for the good of the public but based on their own desire and that their existence as writers may cause them to live too much in fantasy. Nathanael clearly has trouble differentiating reality and his insanity, and even as a child found it hard to stop depicting The Sandman through drawings and turning his existence over mentally. The narrator writes at length about his supposed reasons for writing the story, having heard it and feeling internally pressured to tell it to the public. Hoffmann evidently felt something of the same if he himself truly imagined and wrote the story. However, it can be said of all of them that living in this fantasy world in which they find fantastical stories so important could be damaging to their perception of the reality around them.
Society and Etiquette
Hoffmann parodies society and etiquette by demonstrating social response both to Olimpia's presence and then to the reveal of her true nature as an automaton. Hoffmann writes that society is somewhat skeptical of her because of her stilted movement, but accepts her and even lauds her good behavior at their tea parties because she is quiet and yawns seldom. Once she is revealed as an automaton, these same society people attempt to demonstrate that they are not automatons by yawning often and expressing their thoughts, parodying the fact that these social gestures are still not done to make themselves comfortable or truly communicate but because it is acceptable in high society.
Mental Illness
Mental illness is crucial to The Sandman because the reader of the story must constantly assess Nathanael's level of insanity to decide what to believe of the story. Hoffmann also attempts to instill the reader with a sense of the suddenness and overwhelming nature of fits of madness, often using similes of pain and intense heat to describe the feeling of plunging into a fit and depicting visions that may be a mix of hallucination, warped perception, and true perception of a crazy situation - for example, when Spalanzani throws Olimpia's eyes at Nathanael. The use of mental illness to create the sense of the fantastic in the story is important because fantastic stories like this often rely on, and expose mental illness's basis in, lack of trust in one's own or another's experienced sensation and perception.
