Anti-War versus War
Le Guin was very vocal in her opposition to the Vietnam War, and the way in which it troubled her inspired her to write the novella. There is a great deal of tension in the story between those who believe in violence and those who take a path of non-violence. The colonial military regime ruling the colony is for the most part, aggressive and oppressive. Le Guin intended this to be a symbol of the way in which America was acting as an interventionist force in Vietnam. The soldiers in the colonial army are shown to be heavy drug users who need hallucinogens to control their mood because of the actions they are required to take by their superiors.
The native Athsheans are shown in direct contrast to their rulers. They are peace loving and completely without aggression, and, like Le Guin, in favor of a consensus style of government. When they turn to violence in order to oust the colonialists, they are not comfortable with the fact that they were forced to do this. They believe they have done the wrong thing for the right reason, and the landscape of their lives is forever changed because there is now an underlying potential for violence in the future that was never really there before. Le Guin is trying to make the point the the most peaceful community can be changed into something more violent if they are sufficiently threatened, and this is what she believes to be the inevitable result of interventionism.
Colonialism
Le Guin was also vehemently opposed to the idea of colonialism. The Terran colonists are portrayed as people who are tone deaf to the cultures and traditions of the civilization they are colonizing. They also feel that because they are from a civilization that is more developed in terms of mechanization, they are also more developed and superior in general. They do not see the more deeply spiritual and knowledgeable civilization that they are taking over to be developed in the same way and they mistake this different worldly kind of knowledge for ignorance.
Man versus Nature
Le Guin was fascinated by the subject of man's insensitivity towards the natural world. The Athsheans live in symbiosis with the natural world and they are responsible, making sure to integrate their needs with the needs of the planet. They are very ecologically aware. They have particular respect for forests and name their children after the trees.
By contrast, the colonists could not be more opposite. They have almost exhausted the natural resources of Earth for their own uses which is why they are colonizing other planets for the ecological resources that they can tap. One of the main things that they intend to do to the Athean planet revolves around almost complete deforestation. This was another subject that Le Guin was passionate about and for this reason she juxtaposed the ecologically sound and the ecologically unsound civilizations in the novella in order to show the consequences of ecological irresponsibility.
Dream State
The Athsheans believe that they are active participants in their dreams, and that dreams can be controlled and directed by the force of the mind. This means that they can easily tap into their subconscious. Their earthling colonists are unable to do this because they believe that dreams are completely out of the control of their own conscious mind. The leaders of the Athshean society are those who are best able to interpret their own dreams and communicate this knowledge to their people. Le Guin used the theme of dreaming and consciousness to criticize the "nine to five" mentality that she largely disapproved of, and she wanted to show that being in touch with ones own subconscious leads to greater awareness of others, and of community.