Why does Achebe focus on the Trinity?
Many of Achebe's novels focus on the disparity of understanding that exists between the cultures of the native Africans and the culture of Europe. Colonization run amuck in Africa has had devastating effects because the two cultures see the world differently. Europeans have long been influenced by a Judeo-Christian view of the world, heavily influenced by the changing technology of the day. African culture has been influenced by a polygamous view of the world, influenced more by tribal and family relationships.
The Trinity represents both this disparity of understanding and the illogical behavior of Europeans. The Trinity is the most illogical tenet of Christian belief - that God has a son, but no "wife", and that a holy spirit exists separate from both these divine individuals. Christians pray separately to God and to Jesus. For a culture that has always lived with clear hierarchy, and a need to understand who is in charge, this "tri-focal" power is baffling. Symbolically, the Europeans have also come to Africa to colonize, to take control, but they also behave as if they want to "live in harmony" with the Africans. Baffling, and contradictory. The tribal people, even those who accept the new faith, can not reconcile the the confusing nature of the Trinity.
Achebe uses the Trinity as part of his presentation of the conflict between the Christian and Igbo religions in Chapter 16. One of the white missionaries preaches to the Igbo in Mbanta. The episode is rich in mutual misunderstanding. The Christians dismiss the Igbo gods as 'pieces of wood and stone'; they preach instead that there is 'only one true God and He has made the earth, the sky, you and me and all of us'.
Achebe rarely makes explicit narrative judgment on the actions of his characters; instead he uses their speech, actions and shifts of point of view to make implicit comment. Here he uses the Trinity to expose the irony by which the Christian missionary dismisses the Igbo concept of a multidimensional God, yet talks of the Holy Trinity. Okonkwo's reaction is that 'the man was mad', but Nwoye is captivated by the 'mad logic', which seems to offer 'relief' to his 'parched soul'.
The theological arguments underpinning the conflict are developed further in Chapter 21, in the conversation between Akunna and Mr Brown.