In what ways does the idea of progress shape Things Fall Apart by Chinua Achebe? If Unoka, Okonkwo, and Nwoye are symbolic of three successive generations, how does society in Umuofia change over the course of their lifetimes? Where does Ikemefuna fit into this picture?

Things Fall Apart presents a challenge to the positivist idea of history—that conditions continually improve over time—by depicting the change to Umuofia's culture as a result of Christian missionaries. When the novel begins, Okonkwo is a powerful man and a leader in his tribe. He is famous for wrestling and for growing yams, both of which establish his masculinity. Okonkwo lives in opposition to his father before him. His father was a musician and was always poor and asking others for help. Okonkwo resents his father and vows to be nothing like him. In some sense, at least in Okonkwo's mind, his life is better than his father's; he has made progress compared to the generation before him. He hopes that progress will continue with his son Nwoye, but his son is sensitive, unlike Okonkwo. In fact, one of Okonkwo's daughters is his favorite, but he laments that he cannot treat her like a true heir because she is a girl.
Eventually, when the missionaries have taken over the village, Nwoye converts to Christianity—the ultimate disappointment to his father. Okonkwo, after a seven-year exile, has returned to a new world—but not one he sees as better. He looks at the missionaries as interlopers, and he tries to fight their influence to no avail. Instead of fighting for the continuation of his tribe and its way of life, he commits suicide in a gesture that suggests he does not want to live in the world if it is changed to this extent. The white man's comment on Okonkwo's suicide at the end, how it suggests the "pacification" of the tribes, is a comment by Achebe about the ways in which colonialism and influence of the West in Africa may not have been for the best. The imperialists did not necessarily mean progress for the existing cultures (though maybe, in some way, for their own).
Ikemefuna is a hostage taken in by Okonkwo's family early in the novel. Eventually, an oracle says he must be put to death, and instead of staying home, Okonkwo not only accompanies the walk to his execution but actually is the one to draw the machete himself. This is seen by other tribal leaders as highly unusual and inappropriate. I think this incident plays into the trajectory of the novel as described above by indicating that Okonkwo is not necessarily always in line with the expectations and decorum of his tribe. While some other tribespeople support the missionaries' work, Okonkwo does not, as he is more of a traditionalist.

Throughout the novel, Achebe depicts how the traditional Igbo society of Umuofia drastically changes with the advent of European colonization. Unoka and Okonkwo both symbolize the traditional culture of Igbo society. Throughout the story, Unoka is considered a failure throughout his village because he has no titles and dies a debtor. In contrast, Okonkwo illustrates a successful warrior and farmer, who has earned titles and is respected throughout Umuofia. Ikemefuna also symbolizes the traditional Igbo culture. Mbaino has given Ikemefuna to Umuofia as a sacrifice. After living with Okonkwo's family for three years, Ikemefuna pleases his adopted parents and is considered a promising young man. Unfortunately, Ikemefuna dies at the hands of Okonkwo after an oracle decrees his death.
Okonkwo's son Nwoye symbolizes the newer generation of Umuofia, which is intrigued and drawn to Christianity. Nwoye abandons his family and joins the Christian church because he is attracted to the message of Christ. Nwoye is not attached to the traditions of his society and is a portrayed as a sensitive, introspective individual. The deaths of Ikemefuna and the twins, who were left in the wilderness to die, adversely affect his perception of Igbo culture. Christianity also begins to change the traditional Igbo society as typical village pariahs find acceptance in the Christian church. Okonkwo's violent reaction to the European colonization of his homeland results in his suicide. When Okonkwo realizes that Umuofia will not fight the white men, he loses his temper and kills a court messenger. By the end of the novel, the Igbo society has come to terms with the new European presence, and many citizens have joined the Christian church.

Unoka and Okonkwo represent reactions to the traditional ways of life. Unoka did not meet the village's expectations of what a man should be, as he was considered weak. He disliked fighting and lost money. Okonkwo, his son, makes progress with regard to the esteem of the village of Umofia, as he is a prized wrestler and succeeds at making his own money. Ikemefuna, Okonkwo's adopted son, embodies many of the qualities that Okonkwo and the society prize, as he is diligent and loves his adopted father. However, Okonkwo must kill him when his death is decreed by the oracle in the village. When Okonkwo kills Ikemefuna, there is a real and symbolic disruption in the progress that Okonkwo has made. This progress has come at the expense of his humanity, as he has to kill the boy he loves.
Okonkwo's biological son, Nwoye, represents a kind of adaptation to the white Christian society that has taken over the village by the time Okonkwo is older. Nwoye rejects Okonkwo's brand of traditional masculinity, as he embraces Christianity and its message of love. Okonkwo detests this new order, but there is no doubt that in some ways, Nwoye is better suited to the changes that have come to the village than Okonkwo is. In this way, Nwoye represents progress with regard to adapting to the changes that have come to the village.