Things Fall Apart

One theme would be fate and ambition. Okonkwo takes part in Ikemefuna's murder because of pride and ambition. He does not want to be perceived as weak.

Fate and free will would also come into play, as Okonkwo has the choice not to be a part of Ikemefuna's murder, and yet, he chooses to do so..... knowing the effect the act will have upon his family..... particularly, Nwoye.