You are correct - the story of Jonah is actually a work of didactic fiction - a story which attempts to teach something using a fictional story from the author’s imagination. The author of Jonah wants to teach his audience exactly the same thing that Jesus taught his followers: “Love your enemies”. This is a teaching which, at the time this book was written, was bound to meet with intense opposition. Instead of using a fictional debate to teach (as the author of Job did), the author of Jonah chose didactic fiction. In this genre he could use humor, parody, and irony to teach his audience a lesson that was very difficult for them to accept: God loves other nations too, and so must we.
Arguing over whether this event was a believeable miracle or not ignores church’s instructions of analyzing such stories for clues as to what literary form the author was using and what message is being conveyed. The logic that “God can do anything and miracles should never be ruled out” may be true BUT it is way too restrictive in allowing one to analyze and find the author’s meaning in a story. It effectively destroys the author’s ability and right to craft a fictional account as a vehicle of revelation. Most stories contain literary clues as to the type of writing and this story is one of the prime examples of fictional revelation.
Whether the miracle could have occurred or not is not at all germaine to the meaning of the story.
The answer as to the genre of this story is clearly indicated to the reader by way of the setting, the plot, and the tone. The setting of the book is not realistic - a prophet from Israel preaching in Nineveh before the fall of the northern kingdom. The plot of the book is obviously unrealistic. The episode with the fish, the psalm from the belly of the fish, the immediate repentance of the Ninevites, and the whole episode with the castor-oil plant are perfect for a humorous fictional narrative and ludicrous for a historical narrative. And finally, the humorous tone clues us in to the fact that we are reading fiction: Jonah is not anything like the historical Jewish prophets but a
parody of a historical prophet. His total lack of concern for the Ninevites, even after receiving his call, his angry and accusatory tone toward God, and his constant pettiness all make him a delightful fictional creation rather than a serious historical prophet who could only be regarded with contempt.
There is an extensive discussion of Jonah in
this thread (from which most of the above is taken)
