There's a passage that I love near the end of Madeleine L'Engle's "A Wrinkle in Time" (1962) that mentions exactly this idea in the context of a discussion on predestination vs. free will, and not knowing what the future holds.
"There are fourteen lines, I believe, all in iambic pentameter. That's a very strict rhythm or meter, yes?"
"Yes." Calvin nodded.
"And each line has to end with a rigid rhyme pattern. And if the poet does not do it exactly this way, it is not a sonnet, is it?"
"No."
"But within this strict form the poet has complete freedom to say whatever he wants, doesn't he?"
"Yes." Calvin nodded again.
"So," Mrs. Whatsit said.
"So what?"
"Oh, do not be stupid boy!" Mrs. Whatsit scolded. "You know perfectly well what I am driving at!"
"You mean you're comparing our lives to a sonnet? A strict form, but freedom within it?"
"Yes," Mrs. Whatsit said. "You're given the form, but you have to write the sonnet yourself. What you say is completely up to you."
For people who are not from the UK, the last line comes from the shipping forecast[1], a strange British tradition which is much-loved extremely obscure to the unfamiliar.
I love what you say about the form talking back. That captures something absolutely essential. You bring what you bring. The form then makes you do things you didn’t know you could do, tells you things you didn’t know.
I remember when I was in my twenties, trying to write a sonnet sequence, and when I’d just come to the last couplet of the second sonnet, thinking, oh my God, I know what that last line is going to be. I had no idea that was where the sequence was going, but the form had spoken. The form had pushed back.
"There are fourteen lines, I believe, all in iambic pentameter. That's a very strict rhythm or meter, yes?"
"Yes." Calvin nodded.
"And each line has to end with a rigid rhyme pattern. And if the poet does not do it exactly this way, it is not a sonnet, is it?"
"No."
"But within this strict form the poet has complete freedom to say whatever he wants, doesn't he?"
"Yes." Calvin nodded again.
"So," Mrs. Whatsit said.
"So what?"
"Oh, do not be stupid boy!" Mrs. Whatsit scolded. "You know perfectly well what I am driving at!"
"You mean you're comparing our lives to a sonnet? A strict form, but freedom within it?"
"Yes," Mrs. Whatsit said. "You're given the form, but you have to write the sonnet yourself. What you say is completely up to you."