The second scene of Art 1 of King Lear opens with a soliloquy by Edmund in which he is telling himself that he is an excellent specimen of mankind. The most pertinent lines are the following:
Why bastard? wherefore base?
When my dimensions are as well compact,
My mind as generous, and my shape as true,
As honest madam's issue? Why brand they us
With base? with baseness? bastardy? base, base?
Who, in the lusty stealth of nature, take
More composition and fierce quality
Than doth, within a dull, stale, tired bed,
Go to the creating a whole tribe of fops,
Got 'tween asleep and wake?
It is especially interesting that he asserts that being born out of wedlock is actually an advantage because he was conceived at the height of passion. He apparently believes that the amount of ardor involved in a conception has some effect on the character and appearance of the child conceived. What he is saying about himself is apparently true enough as far as it goes. In Act 1, Scene 1, he makes a very good impression upon the Duke of Kent. When the Duke of Gloucester introduces Edmund to Kent and explains that this son is a bastard, he asks, "Do you smell a fault" and Kent replies:
I cannot wish the fault undone, the issue of it being so
Throughout this opening scene Edmund, who must be played by a handsome and graceful young actor, shows his intelligence, courtly manners, modesty, and winning personality. Then with the opening soliloquy in the second act we learn that he thinks just as highly of himself as everybody else, but also that he has a sinister side of his character which he keeps carefully hidden from everybody, including his own father and brother. He is cunning and ambitious. But his cunning and ambition are motivated by his belief that he is so gifted in so many ways that he deserves to have lands and a title. Unlike another Shakespearean villain Richard III, who is ugly and deformed, Edmund is so attractive that men trust him and women fall madly in love with him--which makes him very dangerous.
In creating the character of Edmund, Shakespeare seems to be contradicting what Edmund says about himself in his soliloquy. Edmund may be handsome and intelligent, but the fact that he was conceived sinfully, according to Shakespeare, has marked his character with a permanent stain. If Gloucester committed a wicked deed in conceiving a son out of wedlock, then that wickedness is carried over into the heart of the child. Like father, like son. We can understand why Edmund must be filled with anger and resentment. Even his father makes fun of him in public, calling him a "whoreson" and a "bastard."
Edmund is not exposed as a villain until quite late in the play, when Gloucester's legitimate son Edgar challenges him to a duel.
Draw thy sword,
That, if my speech offend a noble heart,
Thy arm may do thee justice: here is mine.
Behold, it is the privilege of mine honors,
My oath, and my profession: I protest,
Maugre thy strength, youth, place, and eminence,
Despite thy victor sword and fire-new fortune,
Thy valor and thy heart, thou art a traitor;
False to thy gods, thy brother, and thy father;
Conspirant 'gainst this high-illustrious prince;
And, from the extremest upward of thy head
To the descent and dust below thy foot,
A most toad-spotted traitor. Say thou ‘No,’
This sword, this arm, and my best spirits, are bent
To prove upon thy heart, whereto I speak,