by a complex action I mean one wherein the change coincides with a discovery or reversal or both. These should result from the actual structure of the plot in such a way that what has already happened makes the result inevitable or probable; for there is indeed a vast difference between what happens propter hoc and post hoc. A reversal is a change of the situation into the opposite, as described above, At the end of chapter 7. Vahlen and many other exponents of the Politics confine the meaning of “reversal” to the situation in which the hero’s action has consequences directly opposite to his intention and expectation. There is much to be said for this interpretation, which stresses the irony at the heart of all tragedy. But it is too narrow for Aristotle’s theory. All tragedy involves a change of fortune ( μετάβασις ). In a “simple” plot this is gradual; in a “complex” plot it is catastrophic, a sudden revolution of fortune’s wheel. In some of the greatest tragedies, but not in all, this is the result of action designed to produce the opposite effect. this change being, moreover, as we are saying, probable or inevitable— like the man in the Oedipus who came to cheer Oedipus and rid him of his anxiety about his mother by revealing his parentage and changed the whole situation. The messenger for Corinth announces the death of Polybus and Oedipus’s succession to the throne. Oedipus, feeling now safe from the prophecy that he would murder his father, still fears to return to Corinth , lest he should fulfil the other prophecy and marry his mother. The messenger seeks to reassure him by announcing that Polybus and Merope are not his parents. But the effect of this was to change the whole situation for Oedipus by revealing the truth that he a murdered his father, Laius, and married his mother, Jocasta. This reversal is the more effective because it is immediately coincident with the discovery of the truth. In the Lynceus , too, there is the man led off to execution and Danaus following to kill him, and the result of what had already happened was that the latter was killed and the former escaped. Lynceus married Hypermnestra who disobeyed Danaus in not murdering him. Danaus trying by process of law to compass the death of their son Abas was killed himself. The dog it was that died.