After Proteus betrays Valentine to the Duke ("Thus, for my duty's sake, I rather chose/To cross my friend in his intended drift"), the Duke fully satisfies himself that his daughter is indeed planning to elope with the Veronese gentleman instead of marrying the wealthy merchant, Thurio. He perpetrates a ruse on Valentine, pretending himself to be in love with a woman and asking advice on how best to gain her favor. Valentine falls for the trick, assuring the Duke,
That man that hath a tongue, I say, is no man,
If with his tongue he cannot win a woman. (104–5)
Eager to please Silvia's father, Valentine cheerfully explains how best to conceal a rope ladder when approaching the tower where his lover is "imprisoned." The Duke opens Valentine's cloak to discover a love letter to Silvia and "an engine [ladder] fit for my proceeding." The upshot is instant banishment for the gullible Valentine, who is left to lament:
And why not death rather than living torment?
To die is to be banished from myself;
And Silvia is myself. (170–72)
Proteus arrives with "comforting' words ("Time is the nurse and breeder of all good"). He suggests that Valentine accept banishment, satisfying himself with letters to Silvia, which Proteus promises to deliver:
Thy letters may be here, though thou art hence;
Which, being writ to me, shall be delivered
Even in the milk-white bosom of thy love. (248–50)
To end the scene, Shakespeare has Speed and Launce discuss the merits of the latter's loved one, itemized on a sheet of paper which he carries with him.
The dramatic interest in this scene resides in the protracted "entrapment" of Valentine. Rather than accuse him outright of secretly planning to run off with Silvia, the Duke pretends to seek advice from Valentine on how to snare a woman. Imagine the steady building of eagerness on Valentine's part (showing off to his "father-in-law), coupled with the Duke's muted anger while, point for point, he proves to himself the truth of Proteus's accusation. The Duke described himself as ever "shunning rashness," hence the slow and deliberate method he employs. Once sure, however, he is severe:
But if thou linger in my territories
Longer than swiftest expedition
Will give thee time to leave our royal court,
By heaven, my wrath shall far exceed the love
I ever bore my daughter or thyself. (163–67)
Themes from the main plot are then echoed by Launce and Speed. In a very long dialogue about the pros and cons of Launce's lady, the ultimate reason for the choice of this woman is no different from the Duke's preference for Thurio over Valentine as a suitor for Silvia: money. Launce takes the good with the bad, more often turning the bad into the good:
Speed [reading from the list]: "Item: she hath no teeth."
Launce: I care not for that neither,
Because I love crusts. (244–46)
The rationalization can be explained by a later item:
Speed: "Item: she hath more hair than wit,
and more faults than hairs,
and more wealth than faults."
Launce: Stop there: I'll have her. She was mine, and not mine, twice or thrice in that last article. (361–65)
All this time Launce has been delaying Speed from joining his master, for which he'll receive punishment. This minor "betrayal" parallels the knavery of his master:
Launce: Now will he be swinged for reading my letter — an unmannerly slave, that will thrust himself into secrets! I'll after, to rejoice in the boy's correction. (392–95)