An Aphorism and Chiasmus

-From David A. Kent's essay "On the Third Stanza of Keats's 'Ode on a Grecian Urn'" from Donald Keesey's Contexts in Criticism, page 113

I was not sure what the meaning of "aphorism" was, so I looked it up.  Sharon Hamilton in her Essential Literary Terms defines it as, "a terse statement on a serious subject" (20).  I found it interesting that this seemingly simple phrase is an example of both an aphorism and chiasmus. It really makes you appreciate the Formalist point of view when you see that so simple a grouping of words can have so much literary meaning and significance.