Masculinity as a trap
Okonkwo builds his entire identity around a rigid idea of what a man should be: strong, unemotional, successful. That definition leaves no room for adaptation or grief. It works for him in a stable world and destroys him when the world changes.
Colonialism as cultural destruction
The British don't just impose laws. They replace the entire system of meaning that organized Igbo life: spiritual authority, legal structures, social hierarchies. Achebe shows this as a loss, not a neutral historical transition.
The conflict between tradition and change
Not everyone in Umuofia resists the missionaries. Some people, especially those with low status under the traditional system, find the new order better for them. The novel refuses to treat tradition as automatically good or change as automatically bad.
The weight of the father
Okonkwo's relationship with his father Unoka shapes every decision he makes. He runs from Unoka's image so hard that he ends up embodying a different kind of failure. Nwoye does the same thing in reverse, running from Okonkwo.
Who gets to tell the story
The District Commissioner's plan to write about Okonkwo as a minor detail in a colonial history is the novel's sharpest moment. Achebe wrote Things Fall Apart as a direct answer to that kind of erasure. The novel itself is the argument.