Improbable, Impossible, Unthinkable, Fantastic

James Phelan's model of theory construction moves "from the effects of practice to their causes in the construction of the work." This a posteriori model moves "from the particular case to the larger generalization" (16), whereas an a priori model would move from theoretical principles to the judgement of particular works.¹ Thus an a priori critic might, for example, fault a play which does not obey the dramatic unities of time, place, and action; an a posteriori critic would note that great plays successfully ignore these unities. A few a priori definitions and axioms may be necessary, but in general, the virtues of the a posteriori method are clear. The results of an a posteriori method, however, depend greatly on the selection of particular cases. Questions of probability and possibility, for example, are different in different genres and in different particular narratives.

Phelan goes on to distinguish text-external and text-internal modes of probability; this distinction helps to explain Aristotle's somewhat cryptic comment that a poet should prefer "probable impossibilities" to "improbable possibilities": the adjective in each phrase refers to the text-internal mode and the noun refers to the text-external mode. Phelan's distinction encourages an examination of how an author creates a system of probabilities internal to the text, especially when this text-internal system is contrary to the text-external system. It is not always easy, however, to determine what counts as text-external probability, especially when the events in question have to do with the psychology of characters. Moreover, an a posteriori examination of texts suggests the addition of two further modes of narrative probability: the unthinkable and the fantastic.

The Unthinkable: In book 24, after Hektor has been killed, Achilles takes the body and drags it around Troy. Priam (encouraged by a message from Zeus) decides to go to the Greek camp to ask Achilles to return the body (Il.24.171ff). Hekabe is horrified; she asks where his wisdom has gone: "How can you wish to go alone to the ships of the Achaians/before the eyes of a man who has slaughtered in such numbers / such brave sons of yours? The heart in you is iron" (Il.24.202–04).² So far as Hekabe is concerned, Priam's plan is unthinkable.

When Priam comes to Achilles and grasps his knees in supplication, he seems astonished at his own actions: "I have gone through what no other mortal on earth has gone through; I put my lips to the hands of the man who has killed my children" (Il.24.505–07). He has exceeded his own standards of what is thinkable. And Achilles wonders at Priam's courage: "How could you dare to come alone to the ships of the Achaians / and before my eyes, when I am one who have killed in such numbers / such brave sons of yours? The heart in you is iron" (Il.24.519–21).³ Achilles agrees to give up Hektor's body, but he can barely keep himself from violence; he warns Priam not to anger him: "You must not further make my spirit move in my sorrows, / for fear, old sir, I might not let you alone in my shelter, / suppliant as you are; and be guilty before the god's orders" (Il.24.568–70). Achilles has also entered the realm of the unthinkable.

I am not at all sure how to judge the external probability of these actions by Priam and Achilles; internally, however, these actions seem carefully constructed to combine extreme present unthinkability and also retrospective motivation. Often, the unthinkability of an action is signalled by the reaction of characters within the story, as Hekabe does not believe Priam could go to the Greek camp, or as Achilles doubts his own ability to control his anger.

Many narratives include unthinkable episodes. In such an episode, the reader cannot predict the actions of a character, but once the character has acted, the reader can understand how the action is motivated. (If the reader cannot in retrospect understand the motivation, then the action is inconsistent...