Themes
By the time you swear you’re his, Shivering and sighing, And he vows his passion is Infinite, undying – Lady, make a note of this: One of you is lying.
— Dorothy Parker

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
Parker's little poem warns that vows of love come with a catch. When one person swears devotion and the other promises endless passion, she says, someone is lying. It's a cynical wink at how grand romantic promises can hide untruth.
Context reviewed