What literary term is These violent delights have ends?

The phrase "These violent delights have violent ends" is an example of a rhetorical device called chiasmus.

Here's why:

* Chiasmus: A chiasmus is a figure of speech where two phrases or clauses are structured in a way that mirrors each other, but with the elements reversed.

* Application: In the phrase, "violent delights" is mirrored by "violent ends", but the order is reversed. This creates a sense of balance and emphasis.

While the phrase is often attributed to Shakespeare's *Romeo and Juliet*, it's actually a quote from Edmund Spenser's *The Faerie Queen* (Book IX, Canto IX, stanza XL).