Didactic:
A kind of writings intended to teach or instruct. Aesop's Fables, Alexander Pope's Essay on Criticism, John Bunyan's Pilgrim's Progress, are some of the didactic works.
Dramatic Irony:
A dialogue or a situation which conveys one meaning to the I character or characters on stage but its opposite meaning to the audience.
Examples:
When Oedipus, in Oedipus Rex, says, "I, Oedipus, / Whose name is known afar" he believes that he is really renowned for his good activities but the members of audience know that he is opposite to what he believes. Again, when he declares death penalty for the killer of Laius, "I here pronounce my sentence upon his head", he ' does not know that the punishment falls on his own head but the members of audience, because of their prior knowledge of the myth, know it.
In Macbeth, Duncan wonders at the treason of the previous thane of Cawdor who betrayed him in the battle:
There's no art
To find the mind's construction in the face. He was a gentleman on whom I built
An absolute trust.
(Shakespeare: Macbeth, Act I, Scene IV)
Duncan does not know that he has also failed to read the face of Macbeth who will soon murder him. Similarly, when Lady Macbeth, after the murder of Duncan, says—
A little water clears us of this deed.
How easy is it then!
(Shakespeare: Macbeth: Act II, Scene H)
The audience knows that it is not easy. She also comes to know it much later in Act V, Scene I, and says: "Here's the smell of blood still; all the perfumes of Arabia will not sweeten this little hand."
The use of dramatic irony enhances audience's pleasure and its recurrence strengthens unity of action.
