How do you explain "Fate and free will" in Things Fall Apart?

In Chapter 3 of Things Fall Apart,
Achebe writes:

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Unoka was an ill-fated man.  He had a bad
chi or personal god, and evil fortune followed him to the grave, or
rather to his death, for he had no grave.  He died of the swelling which was an
abomination to the earth goddess...He was carried to the Evil Forest and left to
die.

So, the Ibo tribe has a
way of explaining both physical and supernatural causality using fate by way of
chi instead of in terms of free will.  In other words, Unoka was a
lazy man and died a dishonorable death because of his chi, not
expressly because of his choices.  Unoka was pre-determined to be
agbala, to have no titles, and to be buried in the Evil
Forest.

A Westerner might look at it from another
point-of-view: Unoka had free will because he chose to sing and tell stories and not
work.  Unoka chose not to attain titles because he did not accept the culture into which
he was born.  So, his agbala status and dishonorable death are the
result of his rebellion and not due to supernatural causes of chi
or fate.

Okonkwo attempts to determine his own fate.
 Knowing his father was a failure, he works the yam fields twice as hard to compensate.
 However, Okonwko is also a character in a tragedy, both personal and cultural (both he
and his tribe will "fall apart" and die).  In tragedies, characters are engineered for
downfall.  Obviously, as a character, Okonwko has no control over his and his tribe's
death.  Yet, Okonkwo fights to the death, regardless.  So, in a way, he chooses his fate
by beheading the messenger.  He chooses to be placed in a situation which allows him to
be aggressive and violent so as to cause his own self-destruction by violent means
(suicide).

So, overall, I would say that characters in a
tragedy do not have free will, even though they ironically fight to the death in order
to preserve it.  In tragedy, tragic heroes are victims of tragic fate, which is a
combination of outside determinism and bad personal choices.  Okonkwo's death is
foreshadowed early and often so as to create dramatic irony, the principle device which
guides all tragedy.