Villainelle

I cannot choose the wine in front of me.
And yet I can't discount a bluffing play:
The wine in front of you it cannot be.

You think I'm stalling, but you must agree
That while I hope your choice you might betray,
I cannot choose the wine in front of me.

You beat my Turk, a fighting prodigy,
So you might trust your strength to save the day.
The wine in front of you it cannot be.

You beat my Spaniard very skilfully.
So you would put the poison far away:
I cannot choose the wine in front of me.

I know the poison comes from oversea.
Its origin enables me to say
The wine in front of you it cannot be.

I switched the glasses when you couldn't see!
Yet, unresolved, the paradox must stay –
I cannot choose the wine in front of me;
The wine in front of you it cannot be.

(With apologies to William Goldman. It randomly occurred to me in the bath that this particular poetic form and piece of dialogue were a strikingly good fit for each other.)