A person who publishes a book willfully appears before the populace with his pants down.

Millay’s quip treats publication as an act of deliberate exposure. To “publish a book” is not merely to circulate words but to submit one’s inner life—taste, judgment, vulnerabilities, and ambitions—to the public’s gaze and criticism. The crude image (“pants down”) underscores how powerless an author can feel once the work leaves private control: readers may misunderstand, mock, or judge harshly, and the author cannot fully manage that reception. The line also implies a paradox of artistic courage: the writer chooses this embarrassment knowingly (“willfully”), suggesting that literature requires a willingness to risk humiliation in exchange for being heard.