There are many themes in Ender's Game. One theme is the idea of Ethics. How the world deals with the invasion of the Buggers could be considered unethical. The way the children are treated and dealt with is certainly unethical. Yet, in many respects those same people teach ethics. They have a chain of command, they talk about honor and glory. They talk about cooperation, but then they also believe that the ends justify the means. One example of this is when Ender finally stands up to a school bully and beats him up. The boy dies, but there are no consequences for Ender. In fact they don't even tell him he has killed the boy.
Another theme in Card's novel is cultural pride. Each child is from a different part of the world and they are taught to work together as a team. Yet, there are also many references to their heritage and their cultures. We know from how they behave, talk and their physical appearances what nationality they carry in their hearts. Card emphasises the importance of working together as well as retaining the cultural differences that make us unique.
The theme of isolation and lonliness is also carried througout this novel. Co. Graff makes sure that Ender is disliked before he even arrives at Battle School. Ender is a third child and that made him different from birth. Ender's brother, Peter, constantly deemeaned him and made him feel alone.
"Ender's solitude is crucial to his development as a military leader. "His isolation can't be broken," one of the school supervisors says. "He can never come to believe that anybody will ever help him out, ever. If he once thinks there's an easy way out, he's wrecked." As a result, the International Fleet deliberately isolates Ender at the Battle School."
There are also the themes of innocence, intelligence, personal conflict, altruism versus the individual needs, and world unity. Card is a master at making us look within ourselves to try and improve the human condition.