Memory/Documentary
Digression is one of Achebe's main tools. The novel is the story of Okonkwo's tragedy, but it is also a record of Igbo life before the coming of the white man. The novel documents what the white man destroyed. The reader learns much about Igbo customs and traditions; depicting this world is a central part of the novel.
Greatness and ambition
Okonkwo is determined to be a lord of his clan. He rises from humble beginnings to a position of leadership, and he is a wealthy man. He is driven and determined, but his greatness comes from the same traits that are the source of his weaknesses. He is often too harsh with his family, and he is haunted by a fear of failure.
Fate and free will
There is an Igbo saying that when a man says yes, his chi, or spirit, says yes also. The belief that he controls his own destiny is of central importance to Okonkwo. Later, several events occur to undermine this belief, and Okonkwo is embittered by the experience. As often happens with tragedy, the catastrophe comes through a complex mix of external forces and the character's choices.
Masculinity
Masculinity is one of Okonkwo's obsessions, and he defines masculinity quite narrowly. For him, any kind of tenderness is a sign of weakness and effeminacy. Male power lies in authority and brute force. But throughout the novel, we are shown men with more sophisticated understanding of masculinity. Okonkwo's harshness drives Nwoye away from the family and into the arms of the new religion.
Fear
For all of his desire to be strong, Okonkwo is haunted by fear. He is profoundly afraid of failure, and he is afraid of being considered weak. This fear drives him to rashness, and in the end contributes to his death.
Tribal belief
Particularly since one of the threats to Igbo life is the coming of the new religion, tribal belief is a theme of some importance. Igbo religious beliefs explain and provide meaning to the world; the religion is also inextricable from social and political institutions. Achebe also shows that Igbo religious authorities, such as the Oracle, seem to possess uncanny insights. He approaches the matter of Igbo religion with a sense of wonder.
Justice
Justice is another powerful preoccupation of the novel. For the Igbo, justice and fairness are matters of great importance. They have complex social institutions that administer justice in fair and rational ways. But the coming of the British upsets that balance. Although the British claim that local laws are barbaric, and use this claim as an excuse to impose their own laws, we soon see that British law is hypocritical and inhumane. The final events leading up to Okonkwo's death concern the miscarriage of Justice under the British District Commissioner.
Social disintegration
Towards the end of the novel, we witness the events by which Igbo society begins to fall apart. Religion is threatened, Umuofia loses its self-determination, and the very centers of tribal life are threatened. These events are all the more painful for the reader because so much time has been spent in sympathetic description of Igbo life; the reader realizes that he has been learning about a way of life that no longer exists.